It's always worth making note when something like this pops up in an auction. Featured above is an extremely scarce game-used Sandy Koufax jersey. (Auction Link) It dates to his unbelievable 1963 season when he recorded 25 wins and won both the Cy Young and league MVP awards. Per the auction description:
Rarely does a game-worn Koufax jersey appear at auction. His 1955 jersey recently sold for $667,000. Although that jersey was significant for it being worn during his rookie year, this 1963 jersey was donned by the Dodgers ace during one of the greatest single-season pitching performances in the history of the game.