A product of the 1960s, the Mark I Gyrojet uses a 13mm solid fuel rocket in place of a standard cartridge. As the rocket does not need a solid chamber or extractor equipment, the entire pistol can be greatly simplified and made from lightweight materials. Fixed blade front and fixed notch rear sights, front-mounted hammer, "MARK I/Model B" marked on the left side, and a pair of smooth grips. With a hardwood MBA display case, ten dummy rounds of Gyrojet ammunition, and MBA pamphlet.

Excellent overall, retaining 99% plus original black finish with a few minor handling marks. Mechanically excellent. Case is very good with some interior degradation (mainly around the MBA plaque on the lid, and storage and handling marks and some high edge marks.