WWII US Army Air Force Photo Interpreter’s Height Finder in Original Box c. 1941

This wonderful survivor of the the Second World War is a US Army Air Force Austin Type C-1 photo interpreter’s height finder. I have not figured out exactly how this instrument works but it is clear to me this was used by the USAAF personnel analyzed photos to locate enemy targets for bombing. The ability to determine the altitude at which a aerial reconnaissance photo was taken would give bombardiers more accuracy in their bombing runs. It was manufactured by Advertising Displays Inc. The fitted box contains the height finder, original instructions, a “phora chart” (that I believe was used to calibrate the instrument) and two envelopes of spare parts. Everything looks to be complete and in good order. It is marked on the lid: Finder, Height (Photo interpreter’s) / Type C-1 / Property, Us Army Air Force.