Not
cast. Very unlikely to be
fake. Perhaps die damage. Perhaps a
fourree with silver plate de-laminating due to underlying corrosion (as djmacdo wrote). Perhaps both. It would probably be easy to tell in hand.
Do not mix posts about coins with posts about sellers. Except to say they are on the
NFSL or not, there is no reason to mention the seller at all when asking about a coin's authenticity. I know you didn't name them, but you shouldn't have even suggested you might name them later.