Can you tell me what this coin is?

Greenback Ln. near Sunrise Blvd., Citrus Heights CA

Description

I found this, what looks to be an ancient coin of some kind. It could be something very rare. Just not sure. It's very deteriorated. Can anybody help? In size its between a penny & a nickle. I believe it was copper or bronze. With ridges far apart on the sides - similar to our domes & quarters have. Only the ridges are thick. I'm really stumped. I've looked at it with the best magnifier I have & I see a raised picture of something. Just cant figure it out. The coin dealers I've sent pictures to all say it's too deteriorated to tell. That must mean it's really ancient old, right? I appriciate if anyone out there knows anything about this rare find. Thankyou