Question on Keystone marking on M1 Thompson

[Buickman58]

I have searched and can not remember this silly question. Which manufacture stamped the Keystone outline on the front of the nose on Thompson receivers? Asking from something I saw and snapped no pictures, just cant remember.

[Countryboy77]

On Ar15s its Cerro who uses the keystone mark

[Buickman58]

Thanks, it was driving me crazy. Kahr makes the Thompson tribute guns, a friend was talking about them and could not think of the maker.

[benedw60]

Bob from Philadelphia ordnance did it for a few runs back in the early days

[Bridgeport28A1]

I have a Reconbob (Philadelphia Ordnance) produced milled grip mount that is stamped with a Keystone. I believe they were a single production run item.

 

 

The Cerro forge marking is usually described as a keyhole.

Edited August 6, 2022 by Bridgeport28A1

[Buickman58]

Sorry took me a long time to get a picture, I cant own all but never seen this one.

[Buickman58]

Of course cant figure out how to attach it

[reconbob]

Way back in the 1980s I briefly marked the 80% receivers with a Keystone to identify them as Phila Ord. It did not last long because just about everybody asked if they could get a receiver without the Keystone.

 

Bob/Phila Ord

[Countryboy77]

Where did you mark them Bob?

[Buickman58]

Hello Bob,

Thank you for the help, and nice to know. I often get pieces to make display guns and a friend was taking some lend lease parts off one of your older receivers it looks like. I remembered seeing your mark(I believe) on some bolts a bit back. Nice workmanship on the 80%!

[reconbob]

If I recall I marked the receivers on the left side in front of the magazine cutout. I dont remember marking the front like the one in the photo but its so long ago I cant be sure.

 

We make M1A1 Thompson bolts to GI specs and to distinguish them from original bolts they are marked with a keystone on the rear face of the bolt body.

 

Bob