S21 - Military Study Reel - Consolidated Coronado PB2Y -naval aviation reel
U.S. Navy scout- sub killer - air/sea rescue
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 angles of the same plane, while Test Reels (T+Number) test one's knowledge of recognition of different planes.
Reel: excellent with naval aviation sleeve