This is an extremely rare example of an original WWII Navy Oerlikon 20 mm Cannon with its Navy deck mount that was manufactured by the Pontiac Division of General Motors. In 1917/18 the German engineer Reinhold Becker designed the 20 x 80mm round that fired using a "primer ignition" utilized in a in a very large blow back operated machine gun. They were only manufactured in very limited numbers before the war ended, and the design was almost completely forgotten. Then in 1934 the Swiss company of Oerlikon Contraves dusted off Becker’s design and super-sized it to be able to better shoot down the more modern fighters of the 1930s. This gun, which is typically referred to as just "the 20mm Oerlikon", became probably the most effective anti-aircraft cannon of World War 2. During the war it was also used by the British, Americans, German and even the Japanese Navies/Army. Since it functioned as a straight blow back type operation. It used a huge recoil spring that is mounted around the outside of the barrel to delay recoil. The "projectile" itself is massive, measuring at "7 inch" long, weighing 2,000 grains, fired at 2850 fps, with a maximum effective range of approximately 1500 meters with a max firing range of 4500 meters. The complete deck mount/cannon stands approximately 65 inches tall, and the cannon weighs in at approximately 150 lbs with the deck mount, armour plate and cannon cradle easily weighing in at over an estimated 600 lbs, so the whole cannon/mount is massive. These were used on every type of Navy ship from tugboats to PT boats, minesweepers, all the way up to aircraft carriers and everything in between. These are readily seen in the WWII Navy film footage at Pearl Harbor, Midway, and other navy battles. The German Army even employed them in a wheeled/towed version with twin mounts, and the Japanese used an almost identical version in their fighters, such as the famous Zero. So obviously these are a very historically unique and valuable weapon. Originally they used an electronic sighting system mounted on top of the gun that provide the appropriate lead and angle to make effective kill shots, (this example does not include that sight). Unfortunately with the advent of jet fighters in WWII, they rendered this type of weapon as obsolete, and consequently soon after WWII the Navy destroyed almost all of these as scrap and only a very few examples were ever sold to the general public. Most you see are in a U.S. Navy museum some where. The top of the receiver is stamped with a double Navy Anchor proofmark over "20 mm M.G. MECH/MK 4/SER No. 81263". The deck mount, cannon cradle and armour plate are all unmarked. This rare Navy cannon comes complete with one large drum magazine, a small bag of parts and a small poster from the Pontiac Division of GM.

Very fine with the complete cannon retain 98% of it blackish refurbished parkerized finish overall and most of a Navy Gray painted finish on the complete deck mount, gun cradle and armour plate. It appears to be complete, however, for obvious reasons we have test fired or hand cycled this cannon! NOTE: This item is restricted as 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 478.