However, there was no defining line where the use of the Lyman adjustable sight was discontinued, as they continued to appear sporadically throughout the entire range of serial numbers.
On the Auto-Ordnance, Bridgeport produced Thompsons the L style rear sight began to appear on guns at approximately the 80,000 serial number range. The parts that were manufactured in house by Auto-Ordnance were stamped with the letters AO or AOC.Īs production continued the Auto-Ordnance Thompsons, like the Savage manufactured guns, also began to be fitted with the simple stamped fixed L style aperture rear sight. There were many Savage and other subcontractor manufactured parts used to assemble the guns produced at the Auto-Ordnance plant.
The early manufacture Auto-Ordnance, Bridgeport guns, like their Savage counterparts, were fitted with the finned barrel and the adjustable Lyman rear sight. The letters AO preceding the weapons serial number on the left side of the M1928A1 models receiver will easily identify an M1928A1 Thompson that was produced in the Auto-Ordnances Bridgeport, Connecticut plant.Ī similar AO prefix serial number was applied to the rear of the trigger frame. The 1928A1 Thompson Submachine Guns being produced at Auto-Ordnances Bridgeport plant were identical mechanically and in appearance to those being made by Savage in Utica, New York. As a result, the Auto-Ordnance Corporation opened their own factory in 1941 to help fill the Ordnance Departments requirements for the weapon.