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The main housing of a watch. The case comprises the bezel, as well as the lugs – the four protruding ends of the case where the strap or bracelet is attached.

Refers to the assembled components housed inside a watch’s case that make it work. Interchangeable with the term ‘movement’, a calibre is usually referenced by a specific code and number that identifies its origin, type and manufacturer.

A chronograph is a type of watch that allows the wearer to measure separate intervals of time on top of regular time display. A typical chronograph is activated by one or several push buttons that start, stop and reset the interval timer, which can last from a fraction of a second to 12 hours.

Short for ‘Contrôle Officiel Suisse des Chronomètres’ (Official Swiss Chronometer Testing Institute), a non-profit establishment that tests Swiss-made chronometers. For watches to be COSC-certified, they need to meet stringent standards of accuracy and precision. For instance, COSC-certified mechanical watches are only allowed a variation of -4 to +6 seconds per day. Both Rolex and Tudor watches register performance and accuracy that far exceed COSC requirements. Rolex conducts its own in-house quality assessment with the Superlative Chronometer certification that boasts far more stringent standards. (See also: ‘Superlative Chronometer’.)

A component usually found on the side of the case, which allows the wearer to wind the watch. The crown is connected to the rest of the movement via a winding stem.