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).