Looks like a type of shell. I got plenty of pottery if you send me your address in a private message I will send you some. Then you can compare to what you find. Let me know, rock
Its not shell.. or fossil. Almost looks like rusty old metal. But its not. It sounds exactly like ceramics when knocked on other rocks. It actually has bits of charcoal mixed in.. Not sure what it is. Never seen it before.
The design is on both sides and they look just a like and pottery for the norm does not do that. The patina looks like iron deposit on it. It's cool but