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PCRegarding the 1952 Mays PSA 9 ... definitely different cards and flips. Just look closely at the corners of the black inside border around the Mays cards, and at the inside of the corners on the red part of the flips. The corners are square on one and rounded/uneven on the other, etc.
I sent a link to this thread to the seller, told him his auctions were being discussed, and invited him to come on the board and explain these cards.