"GP" or "CP" marking on barrel, is this a military barrel?

So I bought a 1917 without doing too much research beforehand...I know I know. Well my question is, has anyone seen these markings before? I can't find anything on google about them, I'm guessing this is some sort of commercial barrel, what are your thoughts?

https://www.milsurps.com/images/impo.../mLmLhfG-1.jpg

https://www.milsurps.com/images/impo.../nyuhNak-1.jpg

Gun Parts Co. barrel? Not GI for sure.

Looks like a British commercial proof mark.