J-37 US Military Morse Key

Used by US military in WW2, the Korean war and Vietnam era.
Small and light frame made of black phenolic resin. Leaf spring serving as one of the connections. Adjustment screws for lever tension and contact spacing.
This version, KY-116/U, is a J-37 key mounted on a hinged leg clamp, for portable operation.
The key was made by several manufacturers. This one was manufactured by Winslow Tele-Tronics Inc.