Thompson Patent Date Box Magazines: THE COLT ERA

By Roger Herbst

When the Thompson submachine guns were first produced in 1921, there were three production magazine options: the 100-round “C” drum, the 50-round “L” drum, and the 20-round “XX” box magazine. The first box magazines produced were unmarked, typically referred to today as Colt-era Blank magazines. These were quickly followed by the Colt-era Patent Date magazines, so called because stamped on the front of the magazines are the patent dates of three different patents used in their construction. These patent dates are: AUG. 24, 1920; AUG. 24, 1920; and JAN. 11, 1921. These dates are for: patent no. 1,350,619 issued to Oscar Payne on August 24, 1920; patent no. 1,350,646 issued to Theodore Eickhoff, also on August 24, 1920; and patent no. 1,365,234 issued to Theodore Eickhoff on January 11, 1921. Note that the first two patents were both issued on the same date. This becomes significant later in this discussion.

We do not have definitive documentation on who actually stamped out the Colt-era Patent Date magazines. We do know that John’s Machine and Stamping Works Company of Cleveland, Ohio, made 14 sets of XX magazine dies for Auto-Ordnance, and also produced 506 sample XX magazines by late 1920. We also know that the contract Auto-Ordnance signed with Colt’s called for Colt’s to produce 15,000 guns and 15,000 XX magazines. However, the contract does not indicate that Colt’s will actually manufacture the magazines, nor does it mention anything about whether Auto-Ordnance will supply their existing dies (made by John’s) to Colt’s. We do know that Colt’s supplied grit blasting and bluing service to Auto-Ordnance for both drum and box magazines.

So, where does that leave us? Still in unknown territory. We know that the features on the Colt-era Blank and Patent Date XX magazines are the same, including the circular lifter mark under the follower (Figure 1). This indicates that all the Colt-era XX magazines were made with the same dies and processes. These same characteristics are also present on the Shot or Shotshell magazines that were produced in the early 1920’s, which include the same Patent Date information. Therefore, the best way to refer to these Patent Date magazines is probably simply to call them Colt-era Patent Date magazines. Based on current documentation, it appears the Colt-era Patent Date magazines were produced up to 1939, but we have no information about how many were made or how many different orders occurred over the years. A Colt-era XX Patent Date magazine is shown in Figure 2. The information is on two lines, right and left justified.

There are two different versions of the Shot magazines with patent dates, both with the same two-line patent date information as the standard XX magazines, plus a third line indicating that these magazines are for Shot Cartridges (see figure 3). The stamping on these shot mags was also “whited up” at the factory to call attention to their unique character. Due to the longer shot cartridge length, these magazines are deeper front to back than a standard 45 ACP XX magazine.

Note that the first Shot magazine simply says “FOR SHOT CARTRIDGES” while the second says “FOR 18 SHOT CARTRIDGES”. Both magazines have a capacity of 20 rounds. Shortly after the first magazines were put into use, it was discovered that if the magazine was loaded to full capacity, 20 shot cartridges, the first two cartridges would not feed properly, with the paper nose being damaged during the chambering process. If the magazine was loaded to only 18 cartridges, they performed acceptably. Therefore, the maximum load of 18 shot cartridges was adopted, and the markings on the magazine were updated with this information.

THE MAGUIRE/WWII ERA

Russell Maguire acquired the Auto-Ordnance Corporation in the summer of 1939. He planned to immediately begin building Thompson Submachine Guns and sought a company that could produce the guns. He also needed companies who could produce the magazines for the guns. The first company to produce the XX box magazines for Auto-Ordnance during this period was the Mitchell Stamping Company of Philadelphia, Pennsylvania. They created new dies to produce the XX magazines with the same Patent Date information on the face of the magazine. At this time, there is no known documentation indicating how many of these magazines were made.

Even though the information was the same, the Mitchell magazine lettering was much bolder and stamped more deeply. The horizontal spacing was also less consistent than the Colt-era magazines. Unique characteristics include the dash after PATENTED on the first line that is slightly upswept, and the A in AUG following the dash that is slightly canted to the right, almost as if the dash was pushing the top of the letter aside (see Figure 4).

Mitchell also had a unique way of marking the magazines they produced for Auto-Ordnance. Their company initials, MSCO, were stamped inside the bottom of the backstrap of the magazine (see Figure 5). You cannot see this unless you remove the floorplate.

So, we now have two different standard XX Patent Date magazines, one from the Colt-era and one from the Maguire or WWII era. But, as television advertising loves to tell us, “Wait, there’s more.” Auto-Ordnance needed more box magazines for the new Thompson guns, so more XX magazines were ordered from Mitchell Stamping. A new set of marking dies was used for this production run. The layout of the text was more uniform and looked closer to that of the Colt-era font layout, though the stamping is still broader and deeper. They corrected the upswept dash and canted letter A, but for some unknown reason, the August date on line one was changed from “AUG. 24” to “AUG. 20.” This of course is not correct, as no patent was granted on August 20, 1920. This magazine is shown in Figure 6, and also includes the MSCO stamp on the inside backstrap.

Over the years this second run of XX magazines with the August 20 date have been described in various ways, such as Corrected Patent Date or, more appropriately, Incorrect Patent Date. Both the Colt-era and first Maguire-era magazines have been called Repeat Patent Date, which is correct but doesn’t call out the two different eras involved.

The best way to describe the Maguire-era Patent Date magazines is calling them either Maguire- or WWII-era 24/24 and 20/24. This avoids adjectives that have been misused in the past, and points to the most obvious difference between the two production runs. The Colt-era Patent Date magazines can simply be referred to in those terms for the standard XX magazines. The Shot or Shotshell magazines are typically described as just that, but further clarification is necessary to differentiate the two versions, either FOR SHOT CARTRIDGES or FOR 18 SHOT CARTRIDGES. The latter are more common than the former.

Eventually, Auto-Ordnance switched from the Patent Date markings to a more generic three-line corporate marking, with “AUTO-ORDNANCE CORP.” on the first line, “BRIDGEPORT, CONNECTICUT” on the second line (their new corporate address), followed on the third line with “REG. IN U.S. PATENT OFF.” This is the same manufacturer marking that Auto-Ordnance used on the drum and box magazines that were made later for Auto-Ordnance by United Specialties Company in Chicago, Illinois. Mitchell Stamping continued making magazines for Auto-Ordnance during WWII, but became a subsidiary of United Specialties.

More information on Thompson magazines can be found in the author’s new book with the current working title, “Feeding the Dragon: A Collector’s Guide to Thompson Drum and Box Magazines” due out by the spring of 2022.