Manufactured in the 1960s, the Mark I Gyrojet uses a 13 mm solid fuel rocket in place of a standard bullet and cartridge. As the rocket does not require a solid chamber to contain ignition nor extractor equipment to eject a casing, the entire pistol is greatly simplified and constructed from mostly lightweight materials. Features adjustable blade front and fixed notch rear sights, front-mounted hammer, "MARK I/MODEL B" marked on the left side, and a pair of smooth walnut grips. Includes a MBAssociates "Rocketeer" box.

Excellent overall, retaining 98% original black finish with limited handling marks and minor edge wear on the bottom of the grip frame and slide. Grips are also excellent with minimal handling evidence. Mechanically excellent. Box is fine with storage and handling wear.