What does “Chronograph” mean?

A chronograph is a watch with a built-in stopwatch, started, stopped and reset with pushers on the side of the case. Elapsed time is shown by a central seconds hand and smaller subdials counting minutes and sometimes hours. Many chronographs also have a tachymeter scale on the bezel or dial for calculating speed over a known distance.

Well-known examples include the Rolex Cosmograph Daytona and the Omega Speedmaster. Chronograph movements are more complex than time-only ones, so servicing costs more and originality checks go further: pushers, subdials, hands and movement should all be correct for the reference. Check that the chronograph starts, stops and resets cleanly to zero. Variants such as flyback and split-seconds (rattrapante) chronographs add further functions and are valued accordingly.

Example: 'Chronograph starts, stops and resets to zero, pushers original.'