Developed in the 1930s, the Type 99 was the go-to 20mm autocannon for Japanese military aircraft, serving as the wing guns, flexible mounts and powered turret mounts on a number of Japanese fighters and bombers, including the A6M "Zero" carrier-launched fighter of Pearl Harbor fame. Like many combatants on both sides of the Axis/Allies divide, the Japanese design directly follows the pattern established by the Oerlikon autocannon, using an advanced primer ignition (API) mechanism to reduce the amount of breech locking needed to fire the potent 20mm cannon round while also permitting a high rate of fire. This Mark 1 cannon is configured for the flexible defensive mount role, with the mounting point for the (not included) ammo drum on the underside to keep it out of the gunner's line of sight, and an ejector port on top which can be equipped with a shroud (not included) to direct the spent casings to the shooter's right. A heat shield assembly protects the back half of the barrel, the recoil spring, and the bolt extensions, with a ratcheting hand-cracked charging mechanism on the right side. The left side of the trigger housing bears the Japanese model nomenclature, with dual pistol grips and a detachable buttpad. Sights absent.

Very fine, with 85% original black finish, showing areas of wear and spotting along with some light handing marks. Mechanically needs adjustment, as the bolt is currently stuck in the closed position. NOTE: This weapon is a National Firearms Act (NFA), fully transferable Class 3, which is registered with the Bureau of Alcohol, Tobacco, Firearms and Explosives, (BATFE) that is classified as a "Curios or Relic" as defined in 27 CFR, 478.11. These weapons are still subject to the provisions of 18 U.S.C. Chapter 44 and 27 CFR part 479.