what is this?
we recently pulled this 1939 nickel from a roll and we aren't sure what this is at the top of monticello. will attach photos of both the front and back but what i'm referring to is there on the back at the top of the building. is it some form of die deterioration, deterioration doubling or a damaged die of some kind? we didn't think it appeared to be any kind of post mint damage but really aren't sure what it is. we have been reading/studying various errors and are still fairly new to the study of coins, and struggling to find another example like this. please help us understand what this is. thanks in advance.