A thin Lincoln Cent penny is not a mint error but is the result of a science experiment with nitric acid. The acid causes a chemical reaction to the copper and dissolves the copper until the planchet is ultra thin.
People who find these believe they’re on dime planchets or incorrect planchets or wrong planchet stock or some other mint error. But if you find any or see them for sell then you know these are post mint damaged coins and NOT mint errors with no extra value.
Here’s a video on how it is done.
Related Link: Defective Planchet