Actually it is a RPD. (Re-Punched-Date) An over date would be a digit from a different year was involved. A nice mineral oil bath would help improve your coin. But don't do it until you get the technique down. Try on several other common dirty coin first. The debris on the coin (black stuff) could contain sand. So you have to let it soak for a time to loosen the debris and movement of the grit would need to be careful as sand maybe in the grime and scratch the surface of the coin. A green thorn can be used to carefully loosen the deposits.
Make sure to practice on common coins first.



Make sure you have the technique down first, before working on a valuable coin.
Make sure to practice on common coins first.



Make sure you have the technique down first, before working on a valuable coin.



















