By the Cruver Mfg. Co. Aerial Dead Reckoning Computer. Classic AAF navigational computer with a circular slide rule that can be used to find time, speed & distance, fuel consumption, true airspeed, and density altitude. The wind side of the tool uses a rotating metal azimuth disc marked with 360 degree compass headings, and a sliding grid with speed and angle markings to find wind correction angle, ground speed, true heading etc. This classic design is still used today. This example is well AAF marked and has a 1942 order number/date. In excellent condition with original leather case. Stock code M17119.