It is important to note that this watch bears a tachometer device, which is extremely rare among the different types of military watches made at this period. The graduation of the bezel is in 60 minutes instead of 12 hours as usually found in this series. This model is the most complicated of all the French Military wristwatches: the three registers" Breguet chronograph was developed from the Navy model, with both 15 minutes and 12 hours registers, as well as a continuous auxiliary seconds. An additional feature was the adjustable bezel graduated for 12 hours. The title "retour en vol" refers to the instantaneous fly-back feature of the chronograph work. A single push on the lower chronograph button, zero's the chronograph hand whilst still in motion, which then restarts immediatly, avoiding the need for a pilot to break concentration from the control of the plane.