Spanish Cob?

It looks like a silver crowned shield cob with a jerusalem cross on the other side. If it is dime sized it is probably a 1/2 or 1 reale depending on the actual millimeter size. It would be awesome if you could post better pictures so maybe we can pull an assay mark, mint mark, or date from it. That would help better determine the value. Even in poor condition these are pretty sought after. It really just depends on if you can get more information off of it and how good the details still are. I would also suggest magnet testing it. Cobs are heavily faked. The coloring looks off to me but it could just be the photographs and lighting.

Hope that helps =]