The Fly Reb watch features an external crown with raised numbers positioned counterclockwise and an internal slide rule that can be managed by the crown at "10".
The external crown (Bezel) being with the numbers positioned in reverse on the traditional rings, allows time control with the COUNTDOWN system. In this way the watch reminds the owner how much time is really left to "Time Zero". During a flight, for example, you are in communication with the radar control of the area (CTR) to which you must always communicate an order of pre-established information: who we are, where we come from, where we are flying, next reporting point and final destination. Important for those who fly in VFR (Visual Fligth Rule) or on-sight flight rules, is to communicate the estimated time of the next radio contact that will take place on a particular point in the area called "carry-over" or "fix". This information is easy to manage with the external ring nut giving the count down time to the fix and being able to write the exact time of the carry-over also on the thigh.
The rule allows you to immediately calculate the flight time between 2 fixes (even if already planned and usable as a back up). An additional calculation tool for countless uses.
Antikythera Fly Reb Take Off - Professional Pilot Watch