Manufactured in the 1960s, the Mark I Gyrojet uses a miniature solid fuel rocket in place of a standard cartridge. As the rocket does not need a solid chamber or extractor equipment, the entire pistol is greatly simplified and made from lightweight materials. Fixed blade front and notch rear sights, a sliding magazine cover, front-mounted hammer, model, and caliber on the left side, serial number on underside, and a pair of smooth grips with factory box and operating instructions.