I'll try to inject some more info here. It's fairly flat and no marks where it could of attached to something else.
Take a look at the O O O logo ,blow up the large pic and look.is this some sort icon of a fraternal organization or ?. First thought was a IOOF logo of some sort. A condiment tray or saucer, it could be. This was found today in an 1870's mining town here where I live in Rosita, CO. Was about 6" deep in the county road. They're no makers marks that I can see just the OOO in two places