The Chronograph

A chronograph measures elapsed time alongside the ordinary time display. The long central chronograph hand is not necessarily the watch's running seconds hand: on the two calibres in this catalogue, running seconds occupy a small register.

The mechanism determines the layout

ETA's 7750 has a cam-controlled chronograph with two pushers and seconds, minutes and hours counters. The SW510 M is hand-wound and uses a different arrangement of registers. The 30-minute register moves from twelve on the 7750 to three on the modeled SW510 M. ETA 7750, Sellita SW510 M catalogue, page 71.

Those positions are not freely placed decorations. They reflect where the mechanism drives the hands. For the individual specifications, see Valjoux 7750 and Sellita SW510 M.

Reading a tachymeter

A tachymeter converts elapsed time over one unit of distance into units per hour. If one kilometre takes 30 seconds, 3,600 divided by 30 gives 120 km/h. The same arithmetic works for another consistently measured unit. A scale alone does not create a stopwatch. Oris tachymeter instructions.

A chronometer is a separate concept concerning tested timekeeping performance, not another name for a chronograph.

In the atelier

Selecting Chronograph supplies compatible pushers and the calibre's native registers. The elapsed-time hands are shown at rest; the pushers are not interactive stopwatch controls. Running seconds continue on their own subdial. Changing seconds style or colour changes the central chronograph hand's visual treatment, while the counter furniture remains arranged to keep the dial legible. No timing certification is implied.