@Jay GT4 I have pretty good memory when it comes to coins. The coin that was returned was exactly matching this coin with even the same residual metal (you call it corroded die ) So how could this be explained? You telling me they were minted from the exact the same die ???? If that is the case wow you hit the jack pot my friend otherwise congratulations for an authentic coin I would personally will not keep something that I will always wonder about its authenticity
When there are only a few dies known to exist for very rare issues it is expected to find die matches. Sometimes both obverse and reverse dies will match. I have coins that are die matches for British museum examples or RIC plate coins. Does that make my coins fake? Of course not.