Any Idea on scarcity of this 1818 Half Dollar?

Hey all, I was able to purchase an 1818 Half Dollar that I attributed as an O-107a. I was looking online at the PCGS price guide, and this was the only variety for which a rarity rating was not given. I know the regular O-107 is just an R1, but there didn't seem to be nearly as many examples of the O-107a. Anyone with more experience dealing with CBHs have any insight into the scarcity and potential value of this coin? Thanks!