Colt Firearms manufactured 15,000 Thompson Submachine Guns for the Auto-Ordnance Corporation in 1921, with all 15,000 originally designated Model 1921. They had a cyclic rate of approximately 800 rounds per minute and lacked a muzzle compensator. Between 1926 and 1928, the Marine Corps obtained a few Model 1921 Thompson SMG's, and based on their combat experience in Nicaragua and China, recommended a reduction in the rate of fire to around 600 rounds per minute. In response to the Marines recommendations, Auto-Ordnance modified the bolt, recoil spring and pilot rod to reduce the rate of fire to a more manageable level and added a Cutts compensator to the muzzle to reduce barrel climb during automatic fire. In 1928, Auto-Ordnance redesignated/remarked the modified 1921 guns as "Model 1928". The modified Thompsons' had "U.S. NAVY" stamped above the "MODEL OF 1921" marking on the left side of the receiver and "8" hand-stamped over the "1" in "1921". Although the guns were marked "U.S. NAVY", most Model 1928 Thompsons were sold to law enforcement. This gun has the larger, second style Cutts compensator with Cutts trademarks and patent markings on the top. The gun has the 1928 internal components which include: (1) a 1928 second style blued weighted actuator, (2) long one piece pilot rod. (3) small diameter recoil spring. The gun has the original finned barrel and folding leaf rear sight marked on the base: "MADE BY 'LYMAN' MIDDLEFIELD, CONN. U.S.A." The internal components on the trigger frame and stock are finished bright. The front forearm has been changed to the later horizontal pattern that is marked "S" on the rear indicating it was manufactured by the Savage Arms Company. The left side of the trigger frame is marked "FULL/AUTO" and "SINGLE" along with "FIRE-SAFE" markings, as found on most Colt/AO Model 1928 guns. In addition to the model markings and the serial number "NO 13506", the left side of the receiver is roll-stamped: "THOMPSON SUBMACHINE GUN/CALIBRE .45 AUTOMATIC COLT CARTRIDGE/MANUFACTURED BY/COLT'S PATENT FIRE ARMS MFG. CO./HARTFORD, CONN., U.S.A." in five lines below the rear sight. The right side of the receiver is roll-stamped: "AUTO-ORDNANCE CORPORATION./NEW YORK, U.S.A." in two lines followed by the six-line block of patent dates. The top of the receiver is roll-stamped with the distinctive Thompson "Bullet" trademark. The bottom of the trigger frame is stamped with the matching serial number "NO 13506". Included with this Thompson is: (1) one 50 round "L" Auto-Ordnance drum magazine. In the book "Colt Thompson Submachine Guns Serial Number" listing, this example is last listed as being owned by the Jefferson County Sheriffs Office, Hillsboro Missouri, the transferred to the C&S Metal Works, Missouri 1998 on page 1045.

Very fine with 80% plus of the original blue finish overall with edge and high spot wear with light blue loss on the sides of the receiver, upper side area of the trigger housing and compensator, with a mixed brown patina on the underside area of the trigger guard bow and rear of the pistol grip area. The wood components are all in very fine condition with a nice medium brown color overall with minor scratches on the sides. 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.