The differences are as jbuck pointed out. If a 65,66, or67 has a cameo designation, it is most certainly worth a premium. How much is a totally subjective thing.
It can be difficult to tell them outside of the OGP so I would say slabbed would be your better bet unless you feel you can trust the seller.
It can be difficult to tell them outside of the OGP so I would say slabbed would be your better bet unless you feel you can trust the seller.





















