Hi, I just went thru some of my 1981 mint sets and found this nickel. I have never seen anything like this and would some feedback/ideas of what has happened. Thank you everyone!!
Looks like damage from the sealing process for the packaging this is a common occurrence,not an error.
I'd go along with what Potty said as most of the coins selected for mint sets are of the highest quality, so if it happened after/as it was sealed, that would make sense. Umm, if the mint sealed it, would that make it a "mint error?" LOL