Flyback Chronograph?
(retour en vol) A chronograph that can be stopped, reset and restarted with a single push of one button. In a regular chronograph it would take 3 pushes of 2 different buttons to stop, start and restart. Push the top button to start. Push the bottom button to reset, Push the top button a second time to restart. A flyback chronograph allows restart timing immediately without the delay of several pushes. One push of the bottom button accomplishes all of the 3 above functions.