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Horology A ~ Z

Horology C
Cabochon Crown /
Crown / Winder set with a jewel
Calatrava An ornate cross belonging to an ancient Spanish order of knighthood. Adopted as a symbol by the Patek Philippe watch company.
Calendar Watch A watch with a pointer, sub-dial, or aperture that tells the day of the week, the date, and the month, or some combination of these.
Caliber The designation used to indicate different types of movements by a watch manufacturer; usually used in relationship to a number, such as the JLC cal. 889, with the 889 referring to a series of different distinct movements, such as the 889/1 or 889/2. Historically, the caliber number indicated the diameter of the movement.
Cannon Pinion The friction clutch in a watch movement that allows the hands to be set independently of the motion of the gear train.
Carillon A repeater or other striking watch with 3 or more gongs.
Case The metal container holding the watch movement; usually in steel, gold, titanium, or platinum. Older watches were often cased in silver.
Case Back The underside of a watch. Usually signed by the brand, a recent trend has been to make case backs transparent, i.e., featuring a synthetic crystal that allows a view of the movement.
Central Seconds A second hand located in the center of the dial, as opposed to sub-seconds. Central seconds are divided into two types, direct and indirect, referring to whether the second hand is part of the wheel train's power flow; if not, it is indirect.
Chablon French term for a watch movement (not including the dial and hands), of which all or part of the components are not assembled.
Chamfer Rounding the sharp edges of a watch's parts, notable for aesthetic reasons.
Chaton A metal ring holding a jewel-bearing. Chatons are riveted or screwed into plates, bridges and bars. Their original purpose was mainly aesthetic.

A watch featuring an additional stopwatch function. Chronographs have 2 separate, and independent, time systems. One tells the time of day; the other functions like a stopwatch and measures intervals of time.

Most modern chronographs have 2 pushers: One starts and stops the timing; the other resets the hands to zero when the timing is stopped.

Chronometer / C.O.S.C. To become certified as a chronometer by the COSC, a watch must pass stringent, internationally agreed-upon tests relating to its accuracy. The COSC is a Swiss government agency that tests watches to guarantee they can time within an acceptable error rate. The watch is tested in 5 different positions (dial up, dial down, crown down, crown left, and crown right) and at temperatures replicating the conditions under which the watch will be worn.
Clock-watch A watch with a mechanism which strikes the time in passing, unlike a repeater which strikes the on demand.
Cloisonné A decorative enameling technique using tiny threads of gold to separate various colors to create a design or image. Sometimes used for finer watch dials or cases.
Club-toothed lever escapement Refer to Swiss lever escapement.

Coaxial escapement which was invented by George Daniels and recently implemented by Omega.

The coaxial escapement is more complex than the traditional lever escapement; it has more parts and requires more precise adjustment. On the other hand, it is theoretically not capable of being affected by the influence of lubrication. It also features a smaller angle of interaction between the pallet fork and the balance wheel, thus minimizing another disturbing influence to the timekeeping.

Coin Watch A watch movement inserted inside a coin, which then serves as the watchcase. Usually the coin, most often an older gold piece, is fitted with lugs and a normal band; sometimes the watch stands alone as a pocket watch.
Corum helped pioneer the trend, but other brands have also manufactured them.
Column Wheel A control mechanism consisting of a wheel with ratchet teeth on the bottom and vertical columns on top; traditionally it was employed by finer chronograph movements to coordinate the start, stop, and reset functions.
Complication A basic watch tells time; extras such as the day, the date, or the month are generally called complications. Other complications include a chronograph function, a power-reserve indicator, an alarm, and a moon-phase indicator. Rarer, and therefore more valuable, complications include a tourbillon and a repeater.
CÔTES DE GENÈVE A regular decorative pattern of parallel waves, usually on the movement bridges; sometimes referred to as Geneva stripes.
Crown A knob on a watchcase that winds the mainspring in mechanical watches. The crown also sets the time, and at a different position, sometimes the day and date.
Crown Guards Protrusions from the side of the case next to the crown to protect it from getting knocked or bent on sports watches.
Crystal A transparent cover made of glass, plastic, or synthetic sapphire that protects the dial. (Synthetic sapphire is actually crystallized aluminum oxide.) Although most crystals today are scratch resistant, they are not scratch proof, they are not as hard as a diamond, and some substances can leave marks.
Curb Pins The pins on the regulator that restrict the hairspring and control its effective length, consequently determining the rate of the watch. Also known as regulating pins.
Cyclops The small lens on a crystal that magnifies the date.

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