Sotheby’s is having an auction of Old Masters Drawings on January 28, but don’t expect to put that Hans Bock the Elder on your charge card. Until the end of 2008, Sotheby’s accepted plastic for auction purchases (Eli Broad famously charged his $2.47 million purchase of Roy Lichtenstein’s painting I … I’m Sorry with his American Express card in 1995), but now they’re taking only checks, wire transfers, and cash. Sotheby’s never announced the change publicly, and instead has been noting it in a discreet sign perched on its lobby desk. Putting an auction item on a card “was not widely utilized,” explained a Sotheby’s spokesperson, who also confirmed that the Sotheby’s-branded MasterCard, which offered “privileged access to Sotheby’s experiences and distinctive services, benefits and rewards,” has been discontinued. But, for those who can’t stop charging, Christie’s, on the other hand, started taking credit cards last fall at its New York auctions for purchases of up to $100,000.