Carrera 12 (18k gold) 2456 — Second Execution, Tachymeter Dial (T)

Valjoux 72

13-ligne hand-woundManual windingWinding a mechanical watch’s mainspring by turning the crown. Some automatic movements also allow manual winding. chronographChronographA watch function for starting, stopping and resetting an elapsed-time measurement independently of the ordinary time display. with column wheelColumn wheelA chronograph control system that coordinates the operating levers; a cam system is an alternative construction. and horizontal clutchA chronograph coupling that engages toothed wheels by moving them sideways into mesh. Also called a lateral clutch. It describes the coupling, separately from the column-wheel or cam system that controls it., descended from the 14-ligne Valjoux 22/23. Its 12-hour counter at six set the classic three-register layout. Made 1938–1974 and used by Rolex, Heuer and many others; Rolex fitted it to the pre-Daytona ref. 6234.