A mirrorlike finish for a coin more than 100 years old? So shiny? That "DEALER" is scamming you! Logically, how can that be possible? It is either polished or fake altogether!
I'm having a real hard time believing that the person offering this coin is an actual "dealer", but is more likely either some schmo hawking coins, or we are not getting the whole or correct story from the OP. This isn't to say all true dealers are on the up and up, of course, but the story just smells to bad for buying. If actually offered as a "proof" as opposed to, perhaps, being misrepresented as "proof-like", the asking price should be fairly substantial. No offense to the OP, but he doesn't appear to be that familiar with coins, so it is not outside the realm of possibilities that some sort of misunderstanding could have taken place. Perhaps he has just found a "gem" of a dealer, but without further details, it's probably not wise to assume the worst here.
To me it doesn't matter what the coin actually is... first red flag is that a dealer is telling you it's a proof when no such thing exists... I wouldn't touch the coin even if it is real just because of how heavily polished it is.
I have to say, as far as polished coins go, that is the nicest I have ever seen. Whomever polished that baby has great skills. It's worth melt but I wouldn't mind owning it for silver value, I find it strangely interesting.
Here is my '81 proof. Not my favorite Morgan proof, but still pretty nice. Almost all Morgan proofs were minted in Philadelphia, but there are a few known examples of branch mint proofs (or special strikes) from the New Orleans and Carson City mints. No San Francisco Morgan proofs exist.