Mr. Allen’s trove surpassed the previous, $922m record set in May by New York real-estate developer Harry Macklowe and his ex-wife, Linda Macklowe. Whereas the Macklowe holdings were packed with midcentury masters and pop icons like Andy Warhol, Mr. Allen amassed a museum’s breadth of pieces, from old masters to impressionists to American modernism. The sale had been expected to reach $1b, the house said.