I found it while glancing through my change.
Probably plated in a white medal. Did you weigh it?
Young Numismatist/collectorVisit my eBay store kliao-69
28 Positive BST transactions with 21 members and counting!
It was plated after it left the mint.
A common HS chemistry experiment is to plate cents. Not only does the the student get some hands on experience, they get to take the experiment home. Sometimes they end up back in circulation
Here are some instructions if you want to do it yourself.
May be heat induced.