Found a penny that seems to be missing its copper plating or struck on a different type of metal. Not steel plated tested with magnet. Dont have a scale gonna try to find one at my local coinshop tommarow.
Copper plating was removed post minting. Common. There are threads and photos here that can show you the difference between an unplated cent that gets struck, and a cent that was struck and then had the plating removed.