Flyback chronograph

1928 Longines Wrist-Chronograph with the 1925 modified Cal. 13.33Z Flyback function. The oldest Flyback Chronograph in existence, to be seen in the Museum of Longines.[1]

A flyback chronograph is a watch complication, in which the user can use a reset function without the need to first stop the chronograph, by a single press on an additional pusher at the 4 o'clock mark. In usual chronographs of the time, the user had to push three times for the same operation. First they had to stop the chronograph, then reset the hands at zero, and finally restart the chronograph in order to time the next sequence. A flyback chronograph shortens the time of operation needed to measure subsequent legs of a flight.