Developed by Case on special order from NASA during the 1960s, the M1 survival knife was part of the internal kit of the Gemini and Apollo spacecraft; a common concern in early spaceflight was that landings were made in desolate locations for safety reasons, which could require space crews to hold out on their own until recovery teams arrived. The M1 was designed to be lightweight, versatile, and emit zero fumes. Both knives measure 16 3/4 inches overall, with an 11 3/4 inch round tipped sawback blade marked "PROTOTYPE" and "CASE XX" on the right of knife #1, and the left of #2, and a variant Case logo "C 0000/XX" on the right, full tang hilt and smooth white plastic grips. #1 shows a straight profile to the leading edge, a relatively simple serration pattern, three-line Case Bradford address on the right side, and a rectangular profile to the tang and grips. #2 shows a more aggressive serration pattern, a 2 1/4 inch blade section at the base shaped to act as a prying tool, and more ergonomic contouring of the tang and grips. A set of cardboard protective sleeves are provided in lieu of sheaths.