I do not think it's anything more than a damaged cent. Some chemical or other reactive material or fluid got on this coin. Put two new cents one half on top of the other, and put them on your window sill. You will see something like this happen to the bottom one.
so, what if u just put one of the pennies in the window? Will it become a silver like color? How long would that take? lol
Both sides have it!! Lol! I've seen ones flaking but this one looks pretty cool! Thought possible plating error! ...
Depends, if you put it outside in the summer, with the heat, it will change colors quicker. I actually put gem nickels from the 50's and 60's in old coin envelopes and inside some tupperware. Those have been outside for 2 months. I will be posting these here soon.