This 1965 penny is 20mm diameter and is thinner than your normal penny but weighs 3.1 grams. Could this be a foreign planchet error? Panama. View attachment 91875 6[/ATTACH]
We really can't help you whith just that observation. Struck on foreign planchet errors involves more than just visual and weight. If you can send it to an attributer such as NGC or PCGS.. Fees are high but then you will have your answer.