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Doug Richardson Wants Help

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Doug Richardson wants help: (Revision 1)


I have identified five 1921 Colt receiver variations and three Colt Trigger housings.

The receivers are:

#1: actuator slot with squared front end and “AUT-ORD-CO” bullet logo

#2: actuator slot with rounded front end and “AUT-ORD-CO” bullet logo

#3: actuator slot with rounded front end and “THOMPSON” bullet logo without “REG.


#4: actuator slot with rounded front end and “THOMPSON” bullet logo with “REG. U.S.


#5: actuator slot with rounded front end and “THOMPSON” bullet logo with “REG. U.S.

PAT. OFF.” and 1922 patent dates


The trigger housings are:

#A: “AUTOMATIC” & “SEMI-AUTOMATIC” pivot markings and fire/safe makings

with vertical arrows pointing downward

#B: “AUTOMATIC” & “SEMI-AUTOMATIC” pivot markings and fire/safe markings

with horizontal arrows pointing to front and rear

#C: “FULL AUTO.” & “SINGLE” pivot markings and fire/safe markings with horizontal

arrows pointing to front and rear


Therefore, to completely describe the configuration of a Thompson gun, it could be referred to as a “21 #xxxx 2B with vertical foregrip and ring sight” or “28 Navy #xxxxx 5C with horizontal forearm and compensator”, etc. I don’t know if this reduces or increases the confusion, but at least it is a start. Maybe we will all learn something with this.


It is my theory that the receivers were marked and serialized early in the manufacturing process and therefore will have progressive serial numbers establishing precise, in sequence, cutoffs for each of the five variations described above. It is also my theory that trigger housings were made without serial numbers. They were then placed in stock for selective fit to the receivers when they were finished. For that reason, the three variations of trigger housings will not necessarily correlate exactly to the receiver variations. Obviously, they will generally correlate because guns were being made continuously using the parts being made at the same time. The problem is, there are no records available to tell us at what serial number the changes occurred.


Please, all you guys lucky enough to have a Colt Thompson and even those who only have parts of one, let me know the serial number and the variation it applies to. If you care to include other info such as model marking other than 1921 (e.g. 1927, 1928, 1928 Navy, etc.) or other observations, that would be even more helpful.


Thanks, your help will be greatly appreciated.

TEL: 310-457-6400, FAX 310-457-3010, E/M: ThompsonSMG@mail.com



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I have 1921 Colt - serial # 289 ( matching upper and lower ) as listed on page 63 of Tracie Hill's book.

The receiver is a #1 variation

The trigger housing is a #1 variation


I also have a spare Colt trigger housing serial # 146 and it would fall into the #1 variation of your listings.


Best regards



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To be frank, the law has never been tested.

The attitude is what ever you do , we don't want to know about it and we don't want to hear about it.

One of the problems is the very high cost of ammo.

Also, only C class collectors, dealers and manufacturers are allowed to legally own full auto machine guns and sub-machine guns.

According to my understanding there is nothing to stop the guns from being fired in a controlled range. so as the correct licences are used and correct protocols on the range are used.

Hope this is of some interest,

Kind wishes


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Thanks to all of you who have responded.


A lot of good information has been coming in. To date here are the high and low serial numbers reported for each receiver variation.


1. 41 (starting production number)—2498

2. 2664 - 2796

3. 5278 - 8978

4. 9314 - 13054

5. None reported – 15040 (last production number


I need many more responses to narrow these ranges as you can see. It is interesting that one previously believed range has proven to be in error.


The trigger housings numbers have proven to be all over the place. Naturally variation As are mostly low numbers but variations B & C are almost a mixed random pattern. Interestingly by 2878 and 2889 are Bs but 2885 is a C. 4394 is a C but 6053 is a B.


More data is needed. Please keep sending me information.


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I just checked a couple of 21's I just brought home along with a 1928A1 so her goes:


1921 Ser#26XX is a 2C configuration


1921 Ser#45XX is a 1C configuration


Hope this helps. Unless I read your post wrong the Ser#45XX is an oddball.


Good Luck



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As more responses come in regarding Colt receiver variations 1,2,3,4 & 5 and Colt trigger housing variations A, B, & C that I have previously identified, it becomes increasingly clear that my original belief that receivers were serialized at the beginning of the manufacturing process was wrong. (That is why we do the research instead of making up the “foney facts”.) It seems that Colt receivers and trigger housings must have been completely finished in the white with all markings except the serial numbers. Apparently, they were then selected to fit and serialized. It think it is safe to assume that the lowest number found on a receiver or trigger housing tells us when the change was initiated for that variation (unless an earlier made gun has had the receiver or trigger housing replaced) but does not preclude higher numbers being found on earlier variations of receivers.


Until more responses come in, the following Colt serial number ranges are estimated as follows:


1st Variation: 41-1999

2nd Variation: 2000-4999

3rd Variation: 5000-9999

4th Variation: 10,000-13999

5th Variation: 14000-15040


Trigger Housings

A Variation: 41-2499

B Variation: 2500-2799

C Variation: 2800-15040


I must emphasize that these are roughly estimated ranges subject to refinement. It is not the highest number of a variation that is critical, it is the lowest. Please keep sending the information.




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  • 1 month later...



Two 1921s


sn 694x [why don't people put the whole serial number on?]

Type 3 receiver type 3 lower


sn 730x This is a mismatch--the upper is 730x, and the lower is actually 230x

Type 3 receiver type 1 lower [as 230x]


Sorry reply took so long. Had to get appropriately registered.

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6942 is a 21AC


7308 is the mismatched one--the lower is 2308, beautifully stamped, as all Colts were, but the "2" is scratched over such as would happen by using an electic engraving pencil, to try to make it look like a "7." The "308" are nice and clear.



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