I have posted a few more pictures I think it may be lead .. It was in the ground when they was diggeing the foundations for the cabbort circus buildings
I know it is frustrating to get clear close up photos, but a detailed picture of the design on the face would help. Perhaps if you situated it near a window with the window light shining across the face would help bring out the detail. I tend to agree with ramitt, it looks like a brass or copper signet ring.
It does look quite old, did you say you found it 20 feet deep? If it was in Bristol UK (you don't specify), it might have Roman origins. But living in the States, I have no expertise in Roman artifacts.