This looks like either the planchet had a flaw in it, or a glob of something was on the planchet or the die when struck. The "moon" is flush with the surface of the coin. Any opinions on the nature of the flaw or its value?
I have seen something similar to this on a couple of different Kennedy Half Dollars. No one has ever been able to tell me what it is. Someone once said it looks like a lathe holder mark from the die. Larry Nienaber
Both examples look like a plugged hole, if it isn't on both sides, it would be a partially drilled hole (blind)