By Frank Iannamico
Frank Iannamico has recently finished what is the definitive work on the Military Thompsons. “American Thunder: The Military Thompson Submachineguns” is available from Small Arms Review, we published it. He has also submitted a series of articles on the Identification of the Thompsons- and he thinks it will be a two part series. Hahahahahaha! We plan to chain him to his computer and get a whole series on this. These first two parts cover identifying the Thompsons you are apt to run across in the normal course of being a collector. There were 1919 Thompsons, 1923 Thompsons, 9mm and 30 caliber Thompsons, and all sorts of others, which are well covered in Tracie Hill’s book “Thompson: The American Legend”. In the meantime, please enjoy this series- I have to go email Frank about what his next one will be. Better yet, if you have Thompson articles you want to see, email me at sareview@aol.com, and I will bug Frank about it- Dan
This is part one of a two part series of articles on how to identify a Thompson Submachine by the markings on their receivers.
There are four basic categories of the 1921 and 1928 Thompson Submachine Guns; all were marked with the Auto-Ordnance Corporation name regardless of who manufactured them.
Thompsons manufactured by Colt’s Patent Fire Arms Manufacturing Company from 1921 to 1922. Production Models; 1921A, 1921AC, 1927 Semi-automatic, 1928 “Navy”.
Thompsons manufactured by the Savage Arms Corporation from 1940 to 1944. Models; 1928, U.S. 1928A1.
Thompsons manufactured by the Auto-Ordnance Corporation, Bridgeport, Connecticut from 1941 to 1944. Model; U.S. 1928A1.
Thompsons manufactured by the Auto-Ordnance Corporation, West Hurley, New York from 1975 to 1986. Model 1928.
PART I
The Colt and Savage 1921-1928 Model.
This article is a basic guide on how to identify a particular model and manufacturer of a Thompson Submachine Gun. More detailed information on each variation of these guns will be forthcoming in future articles.
The Thompson Submachine Gun is probably one of the most recognized submachine guns in the world. Even non-enthusiasts are familiar the Thompson. There is however, a lot of confusion on actual manufacturers and other aspects of the guns, especially when the Auto-Ordnance name is mentioned. Adding to the confusion are the more recently manufactured full-auto Thompson guns that were produced by the modern Auto-Ordnance Corporation formerly of West Hurley, New York.
Former U.S. Army Ordnance officer John T. Thompson formed the original Auto-Ordnance Corporation in 1916 with the intent of developing a semi-automatic military rifle dubbed the Auto-Rifle. Work soon shifted to a one-man portable .45 ACP caliber machine gun, that was to become the famous Thompson Submachine Gun. While the famous submachine gun bears Thompson’s name, the weapon was actually designed by Oscar Payne, an employee of Auto-Ordnance. Auto-Ordnance’s Chief engineer, Theodore Eickoff, with the help of his staff, perfected the design into a working weapon. However, without the foresight and fortitude of John Thompson the gun would never have been conceived. The original Auto-Ordnance Corporation was simply a research and development organization, which had no manufacturing facilitates. The Warner and Swasey Company of Cleveland, Ohio manufactured all of the prototype weapons for the Auto-Ordnance Corporation. After a final production model was ready, the manufacture of the weapon was subcontracted out to Colt.
The Colt Thompsons
The very first production Thompsons were manufactured by Colt’s Patent Fire Arms Company of Hartford, Connecticut under contract with Auto-Ordnance from 1921 to 1922. These guns all have the Auto-Ordnance Corporation name and their New York, USA address roll-marked on the right side of the receiver. Also marked on the right side of the receiver near the center, are the patent dates of the Thompson. Early Colt guns have nine patent dates, while later manufacture Colt guns have three additional 1922 dates added. The left rear side of the receiver was marked to announce that Colt’s Patent Fire Arms Co. manufactured the gun, and the .45 ACP caliber of the gun (spelled calibre). The top of the receiver was marked with Auto-Ordnance’s “bullet” logo. Very early manufacture Colt guns under serial number 5000 used a bullet with the name AUT-ORD-CO inside of it. Subsequent receivers were marked with a narrower .30 caliber style bullet, which is often mistaken for an arrowhead, with the name THOMPSON inside of it written in script lettering.
The model designation MODEL OF 1921 was marked on the left side at the center of the receiver. The serial number of the Colt Thompsons was stamped on the left side of the receiver as well as on the trigger frame. Some Colt guns had an additional serial number marked on the receiver under the grip mount. Most Colt guns were inspected and stamped with the initials JHB of John H. Barrett. There were several variations of the Colt Thompson, but all were made from existing 1921 Models, conceived after the initial production run had ended. The “new” models were introduced by Auto-Ordnance in an attempt to generate new interest and increase sales of the guns.
Because of lagging sales Auto-Ordnance introduced a semi-automatic-only version in 1927. The 1927 model was made by the conversion of existing 1921 model guns. Aptly named as the Model of 1927, there were some internal modifications made to eliminate the weapon’s full-automatic operation. The original SUBMACHINE GUN markings were neatly milled off of the gun and replaced with THOMPSON SEMI-AUTOMATIC CARBINE. The words “full auto” were also milled off of the selector markings.
Another variation was the 1928 Navy Model. These were 1921 models that were internally modified to lower the cyclic rate. The Navy guns had the numeral 1 in 1921 over stamped with an 8, and the nomenclature “US NAVY” added above the model designation. The “US NAVY” stamp was usually struck noticeably lighter than the other markings on the receiver. Many of the US NAVY marked guns were used for commercial sales.
World War II
In 1939 the Auto-Ordnance Corporation, now under the control of Russell Maguire, contracted with the Savage Arms Company of Utica, New York to manufacture the Model of 1928 “Like the one illustrated in Auto-Ordnance’s 1936 catalog”. Auto-Ordnance received its first contracts for the Thompson from France and Great Britain. These countries purchased the weapons directly from Auto-Ordnance with no U.S. government involvement. The first Savage manufactured Thompsons were delivered in April of 1940.
The Savage Model of 1928
The contract between Auto-Ordnance and Savage specifically stated that Savage was not to place their name on the Thompsons they manufactured. The early Savage manufactured receivers had Auto-Ordnance’s corporate name and New York, NY address roll-marked on the right side at the rear of the receiver, while the weapon’s thirteen patent numbers* were located at the center of the receiver’s right side. After A-O moved their operation to Connecticut the marking dies were changed to their new Bridgeport address. The Bridgeport address was located at the center of the receiver’s right side, and the patent numbers were moved to the rear of the right side. To date, the highest serial number 1928 model documented with Auto-Ordnance’s New York address has been S-75115, while the lowest serial number 1928 model recorded with a Bridgeport address has been S-83818. Somewhere in-between those two serial numbers the dies were changed to reflect the Bridgeport address of Auto-Ordnance. In addition to the receiver number, a duplicate serial number was stamped on the trigger frame.
*Note; Colt guns had patent dates stamped on them, while Savage and Auto-Ordnance manufactured guns had patent numbers on their receivers. All of the 1921 Colt and all of the WWII 1928 and 1928A1 Thompsons had the word CALIBER spelled as CALIBRE on the left side of the receiver.
Most of the early Savage manufactured 1928 guns were sold to the British. These guns can be identified by a small British proof mark on the receiver and/or barrel. The receiver’s left side was marked “Model of 1928”. There were no U.S. acceptance or inspector’s stamps applied to the British contract guns.
The Savage Commercial
There has been a lot of mystery and confusion regarding the so-called Savage Commercial Thompson. These guns were being made at the same time as the guns for the British contract and were used for the occasional police sales made by Auto-Ordnance in the 1940’s. They are the same as the British contract guns, except there are no British (or U.S. military) acceptance or proof marks on their barrels or receivers. Most of these guns had New York addresses on them, but there have been a few documented with a Bridgeport address.
The Savage U.S. Model of 1928 A1
The United States made the decision to provide military aid to the countries at war with the Axis powers, by passing the Lend Lease Act in March of 1941. Under this program the U.S. government was to take over all foreign contracts with U.S. companies supplying material for the war. One of the provisions of the Lend Lease Act was that all weapons provided under the program be U.S. marked. All future Thompsons would now be marked as U.S. Model of 1928 A1. Thompsons destined for Lend Lease that had already been built, had the U.S. marks added by hand stamping. After the United States entered the war Thompsons were procured by the thousands for U.S. forces, and these guns were virtually the same as the Lend Lease guns.
Early Savage 1928A1 Thompsons that were U.S. marked were stamped US without a period following each letter. The Savage receiver marking dies were changed at approximately the mid S-200,000 serial number range. The changes included the letters U.S. with a period after each letter, and all of the letters of the model designation were more uniform. Use of the new dies resulted in sharp, deeper struck markings than are seen on guns that were marked with the earlier dies.
After the U.S. government began procuring Thompsons, they implemented their own inspection procedures. All weapons were gauged and inspected to insure the guns met the government’s criteria. All Thompsons that passed the inspection process were stamped with the Ordnance Department’s “flaming bomb” stamp. The Ordnance Department’s “flaming bomb” acceptance stamp was superceded by a new Ordnance “crossed cannon” acceptance mark late in October 1942.
The U.S. Army Ordnance officer officially in charge of the entire weapon inspection process was designated as the Army Inspector of Ordnance or AIO. When an AIO’s initials were stamped on a firearm, it indicated that the weapon was accepted as U.S. property by the AIO on behalf of the U.S. Government. The Savage Thompsons were made in the Ordnance Department’s Rochester, NY district. The Army Inspector of Ordnance for the Rochester District were Lt. Colonel Ray L. Bowlin using the stamp, RLB from 1940, until 1942, and Colonel Frank J. Atwood from 1942 until 1945 using the stamp, FJA. Colonel Atwood assumed the position of AIO of the Rochester District near the end of the M1928A1 model production run. His initials are generally only seen on the M1 and M1A1 models.
All Savage manufacture receivers had the Auto-Ordnance “bullet logo” roll marked on the top. A few Savage 1928 models were marked “TOMMY GUN” on the top right of their receivers. This was done to fulfill a legal requirement to register the phrase as a trademark. All Savage manufactured Thompson receivers and frames were marked the GEG initials of Auto-Ordnance’s civilian inspector George E. Goll.
Next; Identifying the Auto-Ordnance, Bridgeport and the Auto-Ordnance, West Hurley Thompsons.

Auto ordnance serial number date. Jump to Latest Follow 1 - 2 of 2 Posts. ForesterPumice Not a Gunsmith, but learning more everyday. Joined Sep 23, 2016 294.

1. It is reported that Auto-Ordnance total production was slightly over 200,000. Serial numbers of Auto-Ordnance manufacture are preceded by 'AO.' The Savage productions has the letter 'S' preceding serial numbers. All production guns were fed by a 20-round box magazines although those adapted prior to the M1 series could use 50-round drum magazines.
2. I just picked up a used thompson in vg+ condition. It has a serial #prefix with KB followed by 4 numbers. Fixed stock, non pistol grip forearm. 16 barrel with pinned compensator. Stamped 'auto-ordnance corporation Worchester, Massachusetts USA Any help would be appreciated.

The letters AO preceding the weapon’s serial number on the left side of the M1928A1 model’s receiver will easily identify an M1928A1 Thompson that was produced in the Auto-Ordnance’s Bridgeport, Connecticut plant. A similar AO prefix serial number was applied to the rear of the trigger frame. The Auto-Ordnance 1911BKO frame incorporates GI specs, and features a matte black finished frame, barrel, and slide. The carbon steel slide, sear, and disconnector are machined from solid bar stock, then heat treated properly to assure durability and long life over many thousands of rounds. The Auto-Ordnance made guns seem to have ended production in the 150,000 + range. Savage stopped production in 1942 before AO did and concentrated on the M1 series. The highest Savage 1928 Model serial numbers are in the 500,000 range. AO only produced the 1928 Model for a about a year, so they made far less guns than Savage. Auto-Ordnance’s 1911BKO has been on the market for a couple of years and is among the best choices for those looking for a well-made “GI 45” that is produced in America and doesn’t break the bank.

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Auto Ordnance Corp Serial Numbers

By Frank Iannamico
During World War II the Savage Arms Company experienced difficulty in keeping up with the ever-increasing demand for more Thompsons. Several attempts were made to simplify the weapon in order to expedite manufacture, but these had limited effects on increasing production.
Auto-Ordnance, Bridgeport
Although all Thompson Submachine Guns have the Auto-Ordnance Corporation name roll-marked on the receiver’s right side, only a small portion of the total production were actually manufactured at the Auto-Ordnance Corporation’s own Bridgeport factory, especially when compared to the total number made. The Auto-Ordnance Corporation had first relied on Colt’s Patent Firearms Manufacturing Company in 1921, and then Savage Arms in 1940 to actually manufacture the Thompson for them. It wasn’t until the autumn of 1941 that Auto-Ordnance opened its own factory, to assist Savage with the overwhelming wartime demand for the weapon.
Russell Maguire opened his Auto-Ordnance factory in a former automotive brake shoe plant located in Bridgeport, Connecticut. The first months after the building was occupied were spent renovating the facilities, and making tools and gauges not already supplied by Savage. By August of 1941, the plant was manufacturing the U.S. M1928A1 model. At first Auto-Ordnance only made receivers and frames in house. Their guns were assembled with parts purchased from Savage and other subcontractors. The plant ran seven days a week and worked two eleven-hour shifts per day. In January of 1942, Auto-Ordnance began to renovate other buildings on the property to further increase production. The Thompsons being produced in Bridgeport were identical mechanically and in appearance to those being made by Savage. All 1928 Thompsons that were made at the Bridgeport factory had with the letters “A.O.” preceding the weapon’s serial number. The serial numbers, like on the Savage and Colt guns, were roll-marked on the center of the left side of the receiver. A duplicate serial number was stamped on the trigger frames, under the stock slide attachment. The marking of the serial numbers on many Auto-Ordnance, Bridgeport guns was rather carelessly done, as the numbers are quite often unevenly spaced and out of line.
The production of Auto-Ordnance, Bridgeport M1928A1 models began approximately sixteen months after Savage. This would mean that a low serial number Auto-Ordnance, Bridgeport M1928A1 would have been manufactured at the same time period as a mid-range Savage M1928A1, and so on. The receiver markings on Auto-Ordnance, Bridgeport Thompsons differ slightly from those on the Savage guns. All 1928 Thompsons manufactured at the Bridgeport factory were US Model 1928 A1’s. The U.S. designation, like early Savage Thompsons had no periods after the letters.
The receivers of Savage Thompsons were roll-marked on the left side “Model of 1928”, while the receivers manufactured by Auto-Ordnance, Bridgeport were marked “Model 1928” without the word “of “ being included. Another detail difference on the receivers was the abbreviation for the word number, stamped before the weapon’s serial number. On Savage Thompsons the abbreviation “NO.” was used, while Auto-Ordnance, Bridgeport guns used the slightly different “No.” abbreviation. The style (font) of the lettering used on the Savage produced Thompsons was also slightly different than that of the Auto-Ordnance guns.
The Auto-Ordnance, Bridgeport plant was under the jurisdiction of the Springfield Ordnance District. Thompson Guns were inspected and proofed by on site Springfield ordnance inspectors. The Army Inspectors of Ordnance or AIOs of the Springfield District during WWII were Colonel Waldemar Broberg and Lt. Colonel Guy H. Drewery. Colonel Waldemar Broberg using the stamp WB, served as AIO of the Springfield District from 1 July 1941 until 30 June 1942. The stamp bearing his initials has been observed impressed on the receiver’s left side above the magazine well area. GHD was the stamp of Lt. Colonel Guy H. Drewery who replaced Colonel Broberg, serving as AIO from 1 July 1942, until 15 July 1945. His stamp was often placed on the receiver’s left side, just forward of the Thompson Submachine Gun logo. The WB inspector’s stamp would be the most common mark encountered on Auto-Ordnance, Bridgeport manufactured US 1928 A1 Thompsons. Colonel Drewery took the position of AIO near the end of the US 1928 A1 model production run at Auto-Ordnance. His initials are primarily only seen on Auto-Ordnance, Bridgeport manufacture M1 and M1A1 models.
An interesting variation of the Auto-Ordnance, Bridgeport produced US 1928 A1 model that has been observed, are those Thompsons that have had the US designation ground off and the numeral “1” of the A1 mark overstamped with a letter “C” to read AC. A letter X was often added as a suffix on the serial numbers of these guns. Interestingly, some of the AO “1928AC” overstamped Thompsons did not have Army Inspector of Ordnance (AIO) acceptance stamps on them, but were stamped with the Ordnance “crossed cannon” acceptance mark. While other examples of these guns had no government acceptance stamps at all, suggesting that they were never inspected or accepted by the U.S. Government. Perhaps these guns were contract overruns or assembled from parts that remained after the government contracts were filled. However, no documentation could be located that could prove or disprove this theory. The Numrich Arms Corporation also removed U.S. markings from original 1928 and 1928A1 model Thompsons they sold in the 1950’s.
The quality, fit and finish of the Auto-Ordnance produced guns was identical to those of Savage manufacture. Interchangeability of parts was 100% as per Ordnance Department directives.
The West Hurley 1928 Model
The Numrich Arms Company of New York purchased the remaining assets of the Auto-Ordnance Corporation in the 1950’s. They were the third company to do so since 1945. Included in the sale were several complete Thompson submachine guns, and a large number of spare parts. Numrich sold many Thompsons that they had assembled from the parts. Many of these guns have NAC added to the serial numbers. These guns were sold to police departments and a few affluent individuals that could afford the $200.00 transfer tax back in the 1950’s. Approximately ten to twelve guns were sold per year until early 1961 when Numrich ran out of critical receivers and frames and no more Thompsons could be assembled.
In 1975 the Numrich Arms Corporation of West Hurley, New York after receiving approval from the BATF, decided to begin manufacture of both semi-automatic-only and full-automatic versions of the Thompson 1928 model, using the Auto-Ordnance name. The receivers, trigger frames bolts and barrels were of new manufacture, while the remainder of the parts used to assemble the early guns were GI surplus. The parts were Savage manufacture, the original Auto-Ordnance, or one of their subcontractors. As production of the West Hurley guns continued, many parts became unavailable, thus forcing the company to manufacture whatever parts they needed to continue production. In the first year of production there were only 199 select-fire 1928 models made.
In addition to the Thompsons the company also produced a thirty-nine round and a fifty round “L” type drum magazines for the guns. Surplus twenty and thirty round GI magazines were also offered. In 1991 the company began a limited run of the coveted one hundred round “C” drum. There were also special commemorative versions of the 1928 Thompson made. Some of the commemorative West Hurley guns were accepted by the BATF for inclusion on their Curio and Relics firearm list.
Most of the 1928 Thompsons manufactured by the modern Auto-Ordnance Corporation of West Hurley, New York were fitted with a compensator equipped finned barrel, vertical foregrip and a replica of the original Lyman adjustable rear sight. The receivers, frames and barrels of the guns were finished with a black oxide, much like the originals had been. Although the majority of the guns had the aforementioned features, special requests were often honored for specially equipped and serial numbered guns. Special order 1928 guns have been documented with and without compensators, rudimentary military “L” and protected “L” style rear sights, as well as military horizontal foregrips. Wide ranges of custom serial numbers were also issued upon a customer’s request. By the time production ceased in 1986 West Hurley Auto-Ordnance had produced a total of 3,306 select-fire 1928 models. Small production runs of a .22 caliber version of the full-automatic 1928 model were also manufactured.
The West Hurley manufactured Model 1928 receivers were uniquely roll-marked as; U.S. MODEL 1928, with the U.S. mark, but lacking the A1 suffix as stamped on the original military guns. The rear of the receiver’s left side was marked THOMPSON SUBMACHINE GUN CALIBER .45M1. This marking was different than the original markings, and the word caliber was not spelled as calibre as the original 1928’s had been. The center of receiver’s right side was marked AUTO-ORDNANCE CORPORATION WEST HURLEY, NEW YORK, U.S.A. The markings on the trigger frame were reminiscent of those of the WWII Auto-Ordnance guns with the words FULL AUTO on one line. The rocker pivot position arrow was also the smaller design of the original Auto-Ordnance frames.

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