I don’t understand why they dock coins for that in the first place. If anything it usually adds character and often eye appeal but I guess that’s subjective. Should be a net neutral either way IMO as far as grade is concerned.
They lower the grades for stuff like that because the slab companies want to make the grades more "generic." They can even put a "details" grade on coins that have mint caused defects that are severe enough. For every collector who is not put off by that reverse alloy mix issue, there are probably three others, if they bid on that coin as an MS-63 or 64, who would feel cheated when they got it. If collectors were given the choice, many would take the coin with no mint caused issues over the perfect one. This is especially true for older 18th and 19th century U.S. coins. When I was dealer I had an 1866 With Rays Shield Nickel in a SEGS holder. The coin was a perfect MS-65 with bright luster and good eye appeal except for one thing. It had a lamination on the obverse. Most of the metal was still hanging from spot. It would hard to think of a coin that was more "Mint State," BUT that defect killed the value of the coin. SEGS mentioned the lamination on the holder, and it was probably in that holder because PCGS, NGC or both companies had refused to grade the piece.
That's a nice FEC, and the discoloration of the planchet doesnt bother me. I would have bought that for ms62 money all day long and been thrilled.
The only thing I can think of that warrants a 62 is that might just be the highest MS grade they will give to any cent with an improper alloy. It seems to me that in a general sense, considering that these issues are, it seems, normally not liked as aesthetically pleasing, that it would downgrade the technical grade.
Say what you will, that is a beauty and the improper alloy area actually looks quite appealing, all things considered.