1921-A with “L” prefix serial number

[Milio]

Hello to all, 

I am searching for information on one of two 1921-A Thompson’s, specifically serial number “L” 1018. Checking G. Herigstad’s Vol 1, Numerical Listings, shows the number as undocumented.
This Thompson has provenance as being presented to an FBI agent by Hoover, and since remained in the same Family.

Specifically, I’m wondering about the letter prefix in the serial number, adamantly stated as being “L1018”, though I cannot find any information referencing an "L" prefix in Thompson numbers.
It is possible the “L” may be a mistaken memory, but considering the source, I’m not too sure of that. I won’t have the piece in-hand until the coming week.

Thank you for reading this, your comments would be appreciated.

Gary

[TD.]

Milio,

L 1018 is not a Colt production serial number. Can you verify if this 1921A is indeed a Colt manufactured Thompson submachine gun. The Colt name and nomenclature will be visible on the left side of the receiver underneath the rear sight - see below with white lettering for easy reference. There are Colt Thompson receivers with serial numbers that were not applied at Colt's. Let's make sure this is Colt Thompson before we go any further. And you may want to ask if it was ever registered with the Internal Revenue Service. 

[Milio]

TD,

Thank you for that. It is my understanding the piece is a Colt, but I will know more next week when I see it in person.

Gary

[TSMGguy]

Photos a must. It's all guesswork without them.

[bug]

11018?

[Bridgeport28A1]

2 hours ago, bug said:

11018?

Well the next question to ask is 11018 listed in Gordon's book?

[Milio]

1 hour ago, Bridgeport28A1 said:

Well the next question to ask is 11018 listed in Gordon's book?

Good thought, shows undocumented as well.

[Milio]

3 hours ago, TSMGguy said:

Photos a must. It's all guesswork without them.

I will post them by next Tuesday. Thanks.

[bug]

What's the SN on the grip frame? Finally, if all else fails pull the barrel.

[Chris Baker]

On 10/4/2025 at 12:38 AM, Milio said:

Hello to all, 

I am searching for information on one of two 1921-A Thompson’s, specifically serial number “L” 1018. Checking G. Herigstad’s Vol 1, Numerical Listings, shows the number as undocumented.
This Thompson has provenance as being presented to an FBI agent by Hoover, and since remained in the same Family.

Specifically, I’m wondering about the letter prefix in the serial number, adamantly stated as being “L1018”, though I cannot find any information referencing an "L" prefix in Thompson numbers.
It is possible the “L” may be a mistaken memory, but considering the source, I’m not too sure of that. I won’t have the piece in-hand until the coming week.

Thank you for reading this, your comments would be appreciated.

Gary

The "L" prefix is indeed unusual for a documented 1921 Thompson. When you get the firearm, carefully check all markings on the receiver and barrel for any clues. It might be an inspection stamp or later-added rack number rather than part of the original serial number.

Edited October 9, 2025 by Chris Baker

[Milio]

16 hours ago, Chris Baker said:

The "L" prefix is indeed unusual for a documented 1921 Thompson. When you get the firearm, carefully check all markings on the receiver and barrel for any clues. It might be an inspection stamp or later-added rack number rather than part of the original serial number.

Thank you, Chris, that's good to know, I appreciate it.
Gary