Howdy, I'm with the Government, and I'm here to help. I thought I would revive this thread.
Just got a 1921 Army issue ser# 8915 b. The dot theory is about to explode. Photo of sideplate with dot. Here's the run down.
Sideplate > 15 Dot
Extractor > 15 Dot centered below number.
Front toggle > 15 Dot
Rear toggle > 15 Dot
Toggle pin > 15 No Dot
Breech block > Dot 15
Holdopen spring > 15 Dot below 5
Takedown > 15 No Dot
Trigger > 15 No Dot
Transfer bar > 15 Dot
Now What
Ron