I agree with John's answer (thanks John!). It could be a mint error, or it could have happened after the mint (which isn't valuable). We can take a look and tell you, the coin would need to be brought in. Thanks!
It could be an error and will need examination by a numismatist. Rare to find - yes and the value may be 10X more not extremely valuable.
Thanks! Your answer is awaiting moderation.