Glossary

ALARM WATCH

A watch provided with a movement capable of releasing an acoustic sound at the time set. A second crown is dedicated to the winding, setting and release of the striking-work; an additional center hand indicates the time set. The section of the movement dedicated to the alarm device is made up by a series of wheels linked with the barrel, an escapement and a hammer striking a gong or bell. Works much like a normal alarm clock.

AMPLITUDE

Maximum angle by which a balance or pendulum wings from its rest position.

ANALOG or ANALOGUE

A watch displaying time indications by means of hands.

ANNUAL CALENDAR

The automatic allowances for the different lengths of each month of a year in the calendar module of a watch.  This type of watch usually shows the month and date, and sometimes the day of the week (like this one by Patek Philippe) and the phases of the moon.

ANTIMAGNETIC

Said of a watch whose movement is not influenced by electromagnetic fields that could cause two or more windings of the balancespring to stick to each other, consequently accelerating the rate of the watch. This effect is obtained by adopting metal alloys (e.g Nivarox) resisting magnetization. Mechanical movements are easily influenced by the magnetic fields often found in common everyday places. This problem is generally solved by the use of anti- or nonmagnetic components in the movement.

ANTIREFLECTION, ANTIREFLECTIVE

A film created by steaming the crystal to eliminate light reflection and improve legibility. Better results are obtained if both sides are treated, but in order to avoid scratches on the upper layer, the treatment of the inner surface is preferred.

ARBOR

Bearing element of a gear or balance, whose end -- called pivots -- run in jewel holes or brass bushings.

AUTOMATIC (or self-winding)

A mechanical watch which does not need to be wound by hand. The movement of the wearer activates a weight which winds the mainspring. A rotating weight, set into motion by moving the wrist, winds the spring barrel via the gear train of a mechanical watch movement.

AUTOMATON

Figures, placed on the dial or case of watches, provided with parts of the body or other elements moving at the same time as the sonnerie strikes. The moving parts are linked, through an aperture on the dial or caseback, with the sonnerie hammers striking a gong.

BALANCE SPRING

Component of the regulating organ, determines the movement's precision. The material used is mostly a steel  alloy (e.g. Nivarox), an extremely stable metal compound, In order to prevent the system's center of gravity from continous shifts, hence differences in rate due to the watch's position, some modifications were adopted. These modifications included Breguet's overcoil (closing the terminal part of the spring partly on itself, so as to assure an almost perfect centering) and Philips curve (helping to eliminate the lateral pressure of the balance-staff pivots against their bearings). Today, thanks to the quality of materials, it is possible to assure an excellent precision of movement working even with a flat spring.

BALANCE

The beating heart of a mechanical movement is the balance. Fed by the energy of the main spring, a tirelessly oscillating little wheel, just a few millimeters in diameter and possessing a spiral-shaped balance-spring, sets the rhythm for the escape wheel and pallets with its vibration frequency.

BARREL

Component of the movement containing the mainspring, whose toothed rim meshes with the pinion of the first gear of the train. Due to the fact that the whole ----made up of barrel and mainspring----transmits the motive force, it is also considered to be the very motor. Inside the barrel, the mainspring is wound around an arbor turned by winding the crown or, in the case of automatic movements, also by the gear powered by the rotor.

BEARING

Part on which a pivot turns, in watches mostly a jewels.

BEVELING

Chamfering of edges of levers, bridges and other elements of a movement by 45 degrees, a treatment typically found in high-grade movements.

BEZEL

An outer ring surrounding the watch dial.

BLUED SCREW

Traditional Swiss and Glashutte watchmaking dictates that a movement should contain blued screws for aesthetic reasons. Polished steeled screws are heated (or tempered, as it is known in watch parlance) to 290 degrees Celsius. This process relaxes the steel, turning it a deep blue in color. Only a few manufactures still put the tempering process in effect with actual heat, others preferring the chemically induced version that assures an even color every time.

BRACELET

A metal band attached to the case. It is called integral if there is no apparent discontuity between case and bracelet and the profile of attachments is similiar to the first link.

BREGUET HANDS

A particular type of hands in a traditional elegant shape.

BRIDGE

Structural metal element of a movement --- sometimes called cock or bar ---- supporting the wheel train, balance, escapement and barrel. Each bridge is fastened to the plate by means of screws and locked in a specific position by pins. In high-quality movements the sight surface is finished with various types of decoration.

BRUSHED, BRUSHING

Topical finishing giving metals a line finish, a clean and uniform look.

CABOCHON

Any kind of precious stone, such a sapphire, ruby or emerald, uncut and only polished, generally of a half-spherical shape, mainly used as an ornament of the winding crown or certain elements of the case.

CALENDAR, ANNUAL

An intermediate complication between a simple calendar and a perpetual calendar. This feauture displays all the months with 30 or 31 days correctly, but needs a manual correction at the end of February. Generally, date, day of the week and month, or only day and month are displayed on the dial.

CALENDAR, FULL

Displaying date, day of the week and month on the dial, but needing a manual correction at the end of the month with less than 31 days. It is often combined with the moonphase

CALENDAR, GREGORIAN

With respect to the Julian Calendar (Calendar, Julian), the calendar reform introduced by Pope Gregory XIII in 1582 corrected the slight erroe of the former calendar by suppressing a leap year every hundred years, except for years whose numbers are divisible by 400 (this entailed the elimination of the leap years in 1700, 1800, and 1900, but not in 2000 and 2400). In non-Catholic countries this reform was introduced after 1700.

CALENDAR, JULIAN

The calendar established by Juilius Caesar was based on the year duration of 365.25 days with a leap year with 366 days every 4 years. In 325 AD, this calendar was adopted by the Church. Due to the slight error (0.0078 day) implied in this time count, the Julian Calendar was later replaced by the Gregorian Calendar (Calendar, Gregorian).

CALENDAR, PERPETUAL

This is the most complex horology complication related to the calendar feature, as it indicates the date, day, month and leap year and does not need manual corrections until the year 2100 (when the leap year will be ignored).

CALIBER

Originally it indicated only the size (in lines, "') of a movement, but now this indication defines a specific movement type and combines it with the constructor's name and identification number. Therefore the caliber identifies the movement.

CANNON

An element in the shape of a hollow cylinder, sometimes also called pipe or bush, for instance the pipe of the hour wheel bearing the hour hand.

CARRIAGE or TOURBILLON CARRIAGE

Rotating frame of a tourbillon device, carrying the balance and escapement. This structural element is essential for a perfect balance of the whole system and its stability, in spite of its reduced weight. As today's tourbillon carriages make a rotation per minute , errors of rate in the vertical position are eliminated. Because of the widespread use of transparent dials, carriages became elements of aesthetic attractiveness

CASE

Container housing and protecting the movement, usually made up of three parts: middle,bezel, and back.

CENTER SECOND HAND

Sweep second hand.

CENTER-WHEEL

The minute wheel in a going-train.

CHAMPLEVE

Hand-made treatment of the dial or case surface. The pattern is obtained by hollowing a metal sheet with a graver and subsequently filling the hollows with enamel.

CHAPTER-RING

Hour-circle, i.e. the hour numerals arranged on a dial.

CHIME

Striking-work equipped with a set of bells that may be capable of playing a complete melody. A watch provided with such a feature is called chiming watch.

CHRONOGRAPH

From the Greek chronos (time) and graphein (to write). Originally a chronograph literally wrote, inscribing the time elapsed on a piece of paper with the help of a pencil attached to a type of hand. Today the term is used for watches that not only show the time of day, but also certain time intervals via independent hands that may be started or stopped at will. A watch capable of recording elapsed time, also called a stop watch.

CHRONOMETER

A high-precision watch that has been awarded an official ring rating certificate for accuracy, having passed a prolonged series of specific tests in a variety of positions and conditions. According to the Swiss law, a manufacture may put the word "chronometer" on a model only after each individual piece has passed a series of tests and obtained a running bulletin and a chronometer certificate by an acknowledged Swiss control authority, such as the COSC.

CIRCULAR GRAINING

Superficial decoration applied to bridges, rotors and pillar-plates in the shape of numerous slightly superposed small grains, obtained by using a plain cutter and abrasives. Also called Pearlage or Pearling.

CLICK

Pawl.

CLOISONNE

A kind of enamel work----mainly used for the decoration of dials----in which the outlines of the drawing are formed by thin metal wires. The colored enamel fills the hollows formed in this way. After oven firing, the surface is smoothed until the gold threads appear again.

CLOUS DE PARIS

Decoration of metal parts characterized by numerous small pyramids.

COCK

A metal plate fastened to the base plate at one point, leaving room for a gear wheel or pinion. The balance is usually attached to a bar called the balance cock.

COLIMACONNAGE

Snailing.

COLUMN-WHEEL

Part of chronograph movements, governing the functions of various levers and parts of the chronograph operation, in the shape of a small-toothed steel cylinder. It is controlled by pushers through levers that hold and release it. It is a very precise and usually preferred type of chronograph operation.

COMPLICATION

Additional function with  respect to the manual-winding basic movement for the display  of hours, minutes and seconds. Today, certain feautures, such as automatic winding or date, are taken for granted, although they should be defined as complications are moonphase, power reserve, GMT and full calendar. Further functions are performed by the so-called great complications, such as split-second chronograph, perpetual calendar, tourbilon device, and minute repeater.

CORRECTOR

Pusher positioned on the case side that is normally actuated by a special tool for the quick setting of different indications, such as date, GMT, full or perpetual calendar.

COSC

Abbreviation of " Controle Officiel Suisse des Chronometres," the most important Swiss institution responsible for the functioning and precision tests of movements of chronometers. Tests are performed on each individual watch at different temperatures and in different positions before a functioning bulletin and a chronometer certificate are issued, for which a maximum gap of -4/+4 seconds per day is tolerated.

COTES CIRCULAIRES

Decoration of rotors and bridges of movements, whose pattern consists of a series of concentric ribs.

COTES DE GENEVE

Decoration applied mainly to high-quality movements, appearing as a series of parallel ribs, realized by repeated cuts of a cutter leaving thin stripes.

COUNTER

Additional hand on a chronograph, indicating the time elapsed since the beginning of the measuring. On modern watches the second counter is placed at the center, while minute and hour counters have off-center hands in special zones, also called subdials.

CROWN-WHEEL

Wheel meshing with the winding pinion and with the ratchet wheel on the barrel-arbor.

CROWN

The crown is used to wind and set a watch. A few simple turns of the crown will get an automatic movement started, while a manually wound watch is completely wound by the crown. Usually positioned on the case middle and allows winding, hand setting and often date or GMT hand setting. As it is linked to the movement through the winding stem passing through a hole in the case. For waterproofing purposes, simple gaskets are used in water-resistant watches, while diving watches adopt screwing systems (screw-down crowns).

DECK WATCH

A large-sized ship's chronometer.

DEVIATION

A progressive natural change of a watch's  rate with respect to objective time. In case of a watch's faster rate, the deviation is defined positive, in the opposite case negative.

DIAL

Commonly called the "face".

DIGITAL

Said of watches whose indications are displayed mostly inside an aperture or window on the dial.

DUAL TIME ZONE

A feature enabling both local time and Greenwich Mean Time to be displayed.

EBAUCHE

Incomplete (jeweled or non-jeweled) watch movement without  regulating organs, mainspring, dial and hands.

ENDSTONE

Undrilled jewel, placed on the balance-staff pivot resting against its flat surface, to reduce pivot friction. Sometimes used also for pallet staffs and escape wheels.

ENGINE-TURNED

Guilloche.

EQUATION OF TIME

The mean time that we use to keep track of the passing of the day 924 hours evenly divided into minutes and not seconds) is not equal to true solar time. The equation of time is a complication devised to show the difference between the mean time shown on one's wristwatch and the time the sun dictates.

EQUINOX

The time when day and night are of equal length, when the sun is on the plane of the equator. Such times occur twice in a year : the vernal equinox on March 21st-22nd and the autumnal equinox on September 22nd-23rd.

ESCAPE WHEEL

A wheel belonging to the mechanism called escapement.

ESCAPEMENT

The part of a watch movement which controls the speed with which energy escapes from the main spring. The combination of the balance, balance spring, pallets, and escape wheel, a subgroup which divides the impulses coming from the spring barrel into small, accurately portioned doses. It guarantees that the gear train runs smoothly and efficiently.

FLINQUE

Engraving on the dial or case of a watch, covered with enamel layer.

FLUTED

Said of surfaces worked with thin parallel grooves, mostly on dials or case bezels.

FLYBACK

A feature which stops a chronograph second hand and returns it to its starting position with a single push of a button. Originally, this function was developed to meet the needs of air forces.

FOLD-OVER CLASP

Hinged and jointed element, normally of the same material  as the one used for the case. It allows easy fastening of the bracelet on the wrist. Often provided with a snap-in locking device, sometimes with an additional clip or push-piece.

FOURTH-WHEEL

The seconds wheel in a going-train.

FREQUENCY

Vibration generally defined as the number of cycles per time unit; in horology it is the number of oscillations of a balance every two seconds or of its vibrations per second. For practical purposes, frequency is expressed in vibrations per hour hour (vph).

FUSEE

A conical part with a spiral groove on which a chain or cord attached to the barrel is wound. Its purpose is to equalize the driving power transmitted to the train.

GEAR TRAIN

A mechanical watch's gear train transmits energy from the mainspring to the escapement. The gear train comprises the minute wheel, the third wheel, the fourth wheel, and the escape wheel.

GENEVA SEAL Poincon de Geneve. GLUCYDUR Bronze and beryllium alloy used for high-quality balances. This alloy assures high elasticity and hardness values; it is non-magnetic, rust-proof and has a very reduced dilatation coefficient, which makes the balance very stable and assures high accuracy of the movement. GMT

Abbreviation for Greenwich Mean Time. As a feature of watches, it means that two or more time zones are displayed. In this case, the second time may be read from a hand making a full rotation in a 24-hour ring (thereby also indicating whether it is a.m. or p.m. in that zone).

GOING TRAIN

Train.

GONG

Harmonic flattened bell in a steel alloy, generally positioned along the circumference of the movement and struck by hammers to indicate time by sounds. Size and thickness determine the resulting note and tone. In watches provided with minute-repeaters, there are often two gongs and the hammers strike one note to indicate hours, both notes together to indicate quarters and the other note for the remaining minutes. In more complex models, euipped also with en-passant sonerie devices, there may be up to four gongs producing different notes and playing even simple melodies (such as the chime of London's Big Ben).

GRAND (or Great) COMPLICATIONS

s. Complication

GUILLOCHE

A surface decoration usually applied to the dial and the rotor using a grooving tool with a sharp tip, such as a rose engine, to cut an even pattern onto a level surface. The exact adjustment of the tool for each new path is controlled by a device similiar to a pantograph, and the movement of the tool can be controlled either manually or mechanically. Real guillochis (the correct term used by a master of guilloche) are very intricate and expensive to produce, which is why most dials decorated into this fashion are produced by stamping machines.

HAMMER

Steel or brass element used in movements provided with a repeater or alarm sonnerie. It strikes a gong or bell.

HAND WOUND

A mechanical watch which must be wound regularly to keep it running.

HAND

Indicator for the analogue visualization of hours, minutes and seconds as well as other functions. Normally made of brass (rhodium-plated, gilded or treated otherwise), but also steel or gold. Hands are available in different shapes and take part in the aesthetic result of the whole watch.

HEART-PIECE

Heart-sheaped cam generally used to realign the hands of chronograph counters.

HELIUM-VALVE

Valve inserted in the case of some professional diving watches to discharge the helium contained in the air mixture inhaled by divers.

HEXALITE

An artificial glass made of a plastic resin.

HUNTER CALIBER

A caliber characterized by the seconds hand fitted on an axis perpenicular to the one of the winding-stem.

IMPULSE

In a lever escapement the action of the escape-wheel tooth on the impulse face of the pallet; in the Swiss lever escapement it is produced by the impulse face of the wheel tooth and that of the pallet.

INCABLOC

Shockproof.

INDEX

A regulating mechanism found on the balance cock and used by the watchmaker to adjust the movement's rate. The index changes the effective length of the balance spring, thus making it move more quickly or slowly.

JEWEL

Precious stone used in movements as a bearing surface. Generally speaking, the steel pivots of wheels in movements turn inside synthetic jewels (mostly rubies) lubricted with a drop of oil. The jewel's hardness reduces wesr to a minimum even over long periods of time (50 to 100 years). The quality of watches is determined mainly by the shape and finishing of jewels rather than by their number (the most refined jewels have rounded holes and walls to greatly reduce the contact between pivot and stone).

JUMPING HOUR

Feature concerning the digital display of time in a window. The indication changes almost instantaneously at every hour.

LEAP-YEAR CYCLE

Leap or bissextile years have 366 days and occur every 4 years (with some exceptions, Calendar, Gregorian). Some watches display this datum.

LEPINE CALIBER

A caliber typical for pocket-watches, characterized by the seconds hand fitted in the axis of the winding-stem.

LIGNE

Line.

LINE

Ancient French measuring unit maintained in horology to indicate the diameter of a movement. A line (expressed by the symbol "') equals 2.255mm. Lines are not divided into decimals; therefore, to indicate measures inferior to the unit, fractions are used (e.g. movements of 13"'3/4 or 10"'1/2).

LUBRICATION

To reduce friction caused by the running of wheels and other parts. There are points to be lubricated with specific low-density oils such as the pivots turning inside jewels, the sliding areas between levers, and the spring inside the barrel (requiring a special grease), as well as numerous other parts of a movement.

LUG

Double Extension of the case middle by which a strap or bracelet is attached. Normally, straps and bracelets are attached with removable spring bars.

LUMINESCENT

Said of materials applied on markers, emitting the luminous energy previously absorbed as electromagnetic light rays. Tritium is no longer used and was replaced by other substances having the same emitting powers, but with virtually zero radioactivity, such as Super-Luminova and Lumibrite.

MAINSPRING

This and the barrel make up the driving element of a movement. It stores and transmits the power force needed for its functioning.

MANUAL

A mechanical movement  in which winding is performed by hand. The motion transmitted from the user's fingers to the crown  is forwarded to the movement through the winding stem, from this to the barrel through a series of gears and finally to the mainspring.

MARINE CHRONOMETER

A large-sized watch enclosed in a box (therefore also called box chronometer) mounted on gimbals and used, on board of ships, to determine the respective longitude.

MARKERS

Elements printed or applied on the dial, sometimes they are luminescent, used as reference points for the hands to indicate hours and fifteen- or five-minute intervals.

MEAN TIME

The mean time of the meridian of the Greenwich Observatory, considered the universal meridian, is used as a standard of the civil time system, counted from midnight to midnight.

MICRO-ROTOR

Rotor.

MICROMETER SCREW

Element positioned on the regulator, allowing to shift it by minimal and perfectly gauged ranges so as to obtain accurate regulations of the movement.

MINUTE REPEATER

A striking mechanism with hammers and gongs for acoustically signaling the hours, quarter hours, and minutes elapsed since noon or midnight. The wearer pushes a slide, which winds the spring. Normally, a repeater uses two different gongs to signal hours (low tone), quarter hours (high and low tone in succession), and minutes (high tone). Some watches have three gongs, called a carillon.

MODULE

Self-contained mechanism, independent  of the basic caliber, added to the movement to make an addditional function available: chrongraph, power reserve, GMT, perpetual or full calendar.

MOONPHASE

A function available in many watches, usually combined with calendar-related features.A disc beneath an aperture on a dial which rotates in synchronization with the phases of the moon.The moonphase disc advances one tooth every 24 hours. Normally, this wheel has 59 teeth and assures an almost perfect synchronization with the lunation period, i.e. 29.53 days (in fact, the disc shows the moonphases twice during a single revolution). However, the difference of 0.03 days, i.e. 44 minutes each month, implies the need for a manual adjustment every two and a half years to recover one day lost with respect to the real state of moonphase. In some rare case, the transmission ratio between the gears controlling the moonphase are calculated with extreme accuracy so as to require manual correction only once in 100 years.

MOVEMENT-BLANK

Ebauche.

MOVEMENT

The "engine" of the watch which drives the hands and other functions. Movements are divided into two great families: quartz and mechanical; the latter are available with manual or automatic winding devices.

NIVAROX

Trade name (from the producer's name) of steel alloy, resisting magnetization, used for modern self-compensating balance springs. The quality level of this material is indicated by the numeral following the name in decreasing value from 1 to 5.

OBSERVATORY CHRONOMETER

An observatory-tested precision watch that obtained the relevant rating certificate.

OPEN-FACE CALIBER

Lepine Caliber.

OSCILLATION

Complete oscillation or rotation movement of the balance, formed by two vibrations.

OVERCOIL

Balance spring.

PALLETS

Device of the escapement transmitting part of the motive force to the balance, in order to maintain the amplitude of oscillations unchanged by freeing a tooth of the escape wheel at one time.

PAWL

Lever with a beak that engages in the teeth of a wheel under the action of a spring.

PERLAGE

Surface decoration comprising an even pattern of partially overlapping dots, applied with a quickly, rotating plastic or wooden peg. Also called circular graining, this embellishment had the original use of preventing dust and dirt from gathering  on the movement's plates. Today it is mainly a traditional type of decoration.

PERPETUAL CALENDAR

A complication which enables a watch to continue displaying the correct date regardless of leap years or short months.

PILLAR-PLATE OR MAIN PLATE

Supporting element of bridges and other.

PINION

Combines with a wheel and an arbor to form a gear. A pinionhas less teeth than a wheel and transmits motive force to a wheel. Pinion teeth (normally 6 to 14) are highly polished to reduce friction to a minimum.

PIVOT

End of an arbor turning on a jewel support. As their shape and size can influence friction, the pivots of the balance-staff are particularly thin and, hence, fragile, so they are protected by a shockproff system.

PLATE

A metal platform having several tiers for the gear train. The base plate of a movement usually incorporates the dial and carries the bearings for the primary pinions of the "first floor" of a gear train. The gear wheels are made complete by tightly fitting screwed-in bridges and bars on the back side of the plate.

PLATED

Said of a metal treated by a galvanizing procedure in order to apply a slight layer of gold or another precious metal (silver, chromium, rhodium or palladium) on a brass or steel base.

PLEXIGLAS

A synthetic resin used for watch crystal.

POINCON DE GENEVE

Distinction assigned by the Canton of Geneva to movements produced by watchmaker firms of teh Region and complying with all the standards of high horlogy with respect to craftmanship, small-scale prouction, working quality, accurate assembly and setting. The Geneva Seal is engraved on at least one bridge and shows the Canton's symbol, i.e. a two-field shield with an eagle and a key respectively in each field.

POWER RESERVE

The amount of time a hand-wound or automatic watch can run without having to be re-wound or worn. Duration (in hours) of the residual functioning autonomy of a movement after it has reached the winding peak. The duration value is displayed by an instantaneous indicator: analog (hand on a sector) or digital (through a wondow). The related mechanism is made up of a series of gears linking the winding barrel and hand. Recently, specific modules wre introduced which may be combined with the msot popular movements.

PRECISION

Accuracy rate of a watch, a term difficult to define exactly. Usually, a precision watch is a chronometer whose accuracy-standard is certified by an official watch rating bureau, and a high-precision watch is a chronometer certified by an observatory.

PULSIMETER CHRONOGRAPH

A scale onn the dial, flange, or bezel that, in conjunction with the second hand, may be used to measure a pulse rate. A pulsometer is always marked with a reference number ---- if it is marked with gradue pour 15 pulsations, for example, then the wearer counts fifteen pulse beats. At the last beat, the second hand will show what the pulse rate is in beats per minute on the pulsometer scale.The pulsimeter scale shows, at a glance, the number of pulse beats per miunte. The observer releases the chrongraph hand when starting to count the beats and stops at the 30th, the 20th or the 15th beat according to the basis of calibration indicated on the dial.

PUSHER, PUSH-PIECE or PUSH-BUTTON

Mechanical element mounted on a case to activate and deactivate functions, such as a stopwatch on a chronograph.

PVD

Abbreviation of Physical Vapor Deposition, a plating process consisting of the physical transfer of substance by bombardment of electrons.

QUARTZ MOVEMENT

A nonmechanical movement powered by a battery. Less expensive than a mechanical movement.

RATCHET (WHEEL)

Toothed wheel prevented from moving by a click pressed down by a spring.

RATING CERTIFICATES

Chronometer and COSC.

REGULATING UNIT

Made up by balance spring, governing the division of time within the mechanical movement, assuring its regular running and abburacy. As the balance works like a pendulum, the balance sprin's function consists of its elastic return and starting of a new oscillation. This combined action determines the frequency, i.e. the number of vibrations per hour, and affects the rotation speed of the different wheels. In fact the balance, by its oscilliations, at every vibration (through the action of the pallets), frees a tooth of the escape wheel ( Escapement). From this, motion is transmitted to the fourth wheel, which makes a revolution in one minute, to the third and then the center wheel, the latter making a full rotation in one hour. However, everything is determined by the correct time interval of the oscillations of the balance.

REGULATOR

A timepiece sufficiently accurate to be used as a benchmark from which to test others. Regulates the functioning of a movement by lengthening and shortening the active section of the balance spring. It is positioned on the balance-bridge and encompasses the balance spring with its two pins near its fixing point on the bridge itself. By shifting the index, the pins also are moved and, by consequence, the portion of the balance spring capable of bringing the baalance back is lengthened or shortened by synchronozing with it, and is thus ready for another recording. Pressure on the split pusher releases the split-second hand, which instantly joins the chronograph hand if the split-second hand happens to be blocked.

RETROGRADE DISPLAY

A retrograde display shows the time linearly instead of circularly. The hand continues along an arc until it reaches the end of its scale, at which precise moment it jumps back to the beginning instantaneously.

ROTOR

The rotor is the component that keeps an automatic watch wound. The kinetic motion of this part, which contains a heavy metal weight around its outer edge, winds the mainspring. It can either wind unilaterally or bilaterally (to one or both sides) depending on the caliber.

SCREW BALANCE

Before the invention of the perfectly weighted balance using a smooth ring, balances were fitted with weighted screws to get the exact impetus desired. Today a screw balance is a subtle sign of quality in a movement due to its costly construction and assembly utilizing minuscule weighted screws.

SKELETONIZATION

The technique of cutting a movement's components down to their weight-bearing basic substance. This is generally done by hand in painstaking hours of microscopic work with a mini hand held saw, though machines can skeletonize parts to a certain degree.

SONNERIE

A variety of minute repeater that---like a tower clock---sounds the time not at the will of the wearer, but rather automatically (en passant) every hour (petite sonnerie) or quarter hour (grande sonnerie).

SPLIT-SECONDS CHRONOGRAPH

Also known in the watch industry by its French name, the rattapante. A watch with with two second hands, one of which can be blocked with a special dial train lever to indicate an intermediate time while the other continues to run.

SPRING BARREL

The spring barrel contains the mainspring. It turns freely on an arbor, pulled along by the toothed wheel interacts with the first pinion of the movement's gear train. Some movements contain two or more spring  barrels for added power reserve.

STAFF or STEM

Arbor.

STOPWORK

Traditional device (now obsolete) provided with a finger piece fixed to the barrel arbor and a small wheel in the shape of a Maltese cross mounted on the barrel cover, limiting the extent to which the barrel can be wound.

STRIKING WORK

Sonnerie and Repeater.

SUBDIAL

Zone.

SUPER-LUMINOVA

Luminescent.

SWEEP SECOND HAND

A center second hand, i.e. a second hand mounted on the center of the main dial.

TACHOMETER or TACHYMETER

A scale on the dial, flange, or bezel of a chronograph that, in conjunction with the second hand, gives the speed of a moving object. The tachometer scale is calibrated to show the speed of a moving object, such as a vehicle, over a known distance. The standard length on which the calibration is based is always shown on the dial, e.g. 1,000, 200 or 100 meters, or ---- in somes cases ---- one mile. As the moving vehicle, for instance, passes the starting-point of the measured course whose length corresponds to that used as the basis of calibration, the observer releases the chrongraph hand and stops it as the vehicle passes the finishing point. The figure indicated by the hand on the tachometer scale represents the speed in kilometers or miles per hour.

TELEMETER

By means of the telemeter scale, it is possible to measure the distance of a phenomenon that is both visible and audible. The chronograph hand is released at the instant the phenomenon is seen; it is stopped when the sound is heard, and its position on the scale shows, at a glance, the distance in kilometers or miles separating the phenomenon from the observer. Calibration is based upon the speed at which sound travels through the air, approximately 340 meters or 1,115 feet per second. During a thunderstorm, the time that has elapsed between the flash of the lightning and the sound of the thunder is registered on the chronograph scale.

THIRD WHEEL

Wheel positioned between the minutes and second wheels.

TIME ZONES

The 24 equal spherical lunes unto which the surface of the Earth is conventionally divided, each limited by two meridians. The distance between two adjacent zones is 15 degrees or 1 hour. Each country adopts the time of its zone, except for countries with more than one zone. The universal standard time is that of the zero zone whose axis is the Greenwich meridian.

TONNEAU

Particular shape of a watchcase, imitating the profile of a barrel, i.e. with straight, shorter, horizontal sides and curved, longer, vertical sides.

TOURBILLON PRINCIPLE

The purpose of the tourbillon is to compensate for the effects of gravity on a mechanical watch. When it is in a vertical position, a mechanical watch’s regulating organ – the balance, balance spring and escapement – undergoes imperceptible errors of rate with each oscillation, due to the effects of gravity. By housing the regulating mechanism in a cage rotating on its own axis, generally once a minute, a variety of vertical positions results, which compensate for each other, producing a very constant average rate and extreme running precision.

Though as good as moot in a wristwatch, this superb horological highlight is seen as a sign of technological know-how in the modern era. Its manufacture, one of the most complex and delicate, necessitates a perfect mastery of watchmaking and its techniques. Although this device is not absolutely necessary for accuracy purposes today, it is still appreciated as a  complication of high-quality watches.

TRAIN

All the wheels between the barrel and escapement.

TRANSMISSION WHEEL

Crown-wheel.

UNIVERSAL TIME

The mean solar time of the Greenwich meridian, counted from noon to noon. Often confused with the mean time notion

VARIATION

In horology the term is usually referred to the variation of the daily rate, i.e. the difference between two daily rates specified by a time interval.

WATER RESISTANT or WATERPROOF

Water resistance is an important feauture of any timepiece and is usually measured in increments of one atmosphere (atm or bar, equal to 10 meters of water pressure) or meters and is often noted on the dial or caseback.The case is designed in such a way to resist infiltration by water (3 atmospheres, corresponding to a conventional depth of 30 meters; 5 atmospheres, corresponding to conventional depth of 50 meters.)

WHEEL

Circular element, mostly toothed, combines with an arbor and a pinion to make up a gear. Wheels are normally made of brass, while arbors and pinions are made of steel. The wheels betwen barrel and escapement make up the so called train.

WINDING STEM

Element transmitting motion from the crown to the gears governing manual winding and setting.

WINDING, AUTOMATIC VIBRATION

Movement of the pendulum or other oscillating bodies, limited by two consecutive extreme positions. In an alternate (pendulum or balance) movement, a vibration is a half of an oscillation. The number of hourly vibrations corresponds to the frequency of a watch movement, determined by the mass and diameter of a balance and the elastic force of the balance spring. The number of vibrations per hour (vph) determines the breaking up of time ( the "steps" of a second hand). For instance, 18,000 vph equals a vibration duration of 1/5 second; in the same way 21,600 vph = 1/6 second; 28,800 vph = 1/8 second; 36,000 vph = 1/10 second. Until the 1950s, wristwatches worked mostly at a frequency of 18,000 vph; later, higher frequencies were adopted to produce a lower percentage of irregularities to the rate. Today, the most common frequency adopted is 28,800 vph, which assures a good precision standard and less lubrication problems than extremely high frequencies, such as 36,000 vph.

WINDOW

Aperture in the dial, that allows reading the underlying indication, mainly the date, but also indications concerning a second zone's time or jumping hour.

WORLD TIME

Additional feature of watches provided with a GMT function, displaying the 24 time zones on the dial or bezel, each zone referenced by a city name, providing instantaneous reading of the time of any country.

ZODIAC

Circular belt with the ecliptic in the middle containing the twelve constellations through which the sun seems to pass in the course of a year.

ZONE

Small additional dial or indicator that may be positioned, or placed off-center on the main dial, used for the display of various functions (e.g. second counters).