Thanks for all the replies, very educational. I'm asking for someone else (inherited pistol). After some more searching after posting this I sort of figured it was european, maybe french although I never found a match. Asking more questions the guy who had this spent a tour on the ground in vietnam confirming suspicions of being european or a european copy (if that's where he got it, that is). The serial number is stamped pretty solidly.
I'll pass on the question about markings on the cylinder.
Another shot of the other side.