Id of proof mark

Can anyone tell me what this is.....

Looks like a letter C or G under a crown.

https://www.milsurps.com/images/impo...3/CrownG-1.jpg
Thanks, Craig

Any chance of getting a more close up look at the mark?

What rifle type and part type is it stamped on?

Thanks... :)

Regards,
Badger

Thompson gun.

Here's perhaps a more close up and clearer views that "missing something" emailed me... :)

Looks like a British Proof Mark to me....

Regards,
Badger

Looks like the entwined GP mark of the London Proof House, a commercial proof mark put on after the arms were surplused. This mark appeared on the CA thompsons sold in the 80s.