Think I found a Gold Ring with my previous post....

Just decided to empty out my junk bag from last water detect and saw what I thought brass ring,like the old curtain ones....but I remembered I saw what looked like a stamp on the inside while in the water
Due to the shape....completely round(not flat on the inside like all rings I've seen) I thought it could not be a ring as it was quite tarnished as well

After some metal polish it came out like this...

Stamp looks like C JK 333  ?
Which leads me to believe it is 8CT gold
What do you guys reckon?