Question for coin collectors

My Grandpa got a Mercury dime the other day and he didnt realize it and the woman at the gas station refused to take it. She said it wasnt real so he gladly took it back. I have found several $1 in change, I have a few that are fromthe 60-70's that I got in change. Sometimes kids take their grandparents change from their closets. There are alot of coins reintroduced to the market that way. But to answer your question no I have no clue. I will be buying Dinars while I am over here though.