Strange Hallmark on old gold wedding band

by Robert Stanley
(Austin TX US)

Found this gold ring in an old shed on some property I bought years ago. There's no karate marking, though I'm sure it's gold, just some strange markings. It starts with what appears to be the letter X in quotes, followed by some sort of design then a 0 (with a line through the center from side to side) in quotes. (x)...(O).

Also, how to I find out the karat?

Thanks
Robert