S38 -Military Study Reel - Mary - naval aviation reel
Imperial Japanese bomber
U.S. Naval Aviation Training Division
Military Study Reels consist of 7 different range and attitude (tilt/angle) images of a plane. These reels were issued to military personnel during World War II, for recognition and range estimation of both enemy and friendly aircraft.
Study Reels (S+Number) contain recognition of different variations of the same plane, while Test Reels (T+Number) test one's knowledge of recognition of different planes.
Reel:: Scattered remnants of dark dis-colored dye spots in the background, barely noticeable in standard viewers.