Looks like a die chip.. Very cool, pretty common though.
From the picture, it actually looks like a different metal was struck into the coin. Either way, a cool find.
More than likely it is a strike through. They are very common with the satin finish coins for some reason.
This is a die clash. You can see jefferson's eyes peeking out from under monticello. Very cool coin, I'd love to find a die clash like this!!!!
That is a pretty large strike through error...and when it is struck through something other than grease they usually have a higher demand. Very cool.
I don't write anything on my 2x2's, I just leave em' blank--in my opinion it looks better. My coin pages are organized by country, then by...
Separate names with a comma.