Going through my fathers coins, i have found an off metal cent that weighs significantly less than other cents and is a couple Millimeters smaller than others as well as half the thickness. The lincoln also appears to have some sort of die clash or lamination error. i am sending tommorow for authentication but wanted some.opinions.
My suspicion would be a coin soaked in acid for a time. Acid reacts on the entire surface and reduces the metal proportionally, so all impressions are reduced almost equally in all directions, so lettering and devices still are visible. A damaged coin. Sorry. Jim