Gary Oldman is among the stars from the Harry Potter films that have agreed to sign autograph cards in Artbox's Harry Potter and the Prisoner of Azkaban Trading Card set, which ships in May.  Michael Gambon, who played Albus Dumbledore, also contributed his signature.  The signature cards are among the approximately 30 cards in the hobby release that are not in the retail set.  Others include props cards, costume cards, and the box and case toppers.  An Artbox spokesperson told ICv2 that the company was producing only a limited number of the Harry Potter cards, and that he expected them to sell out quickly.  An update set is planned for Fall 2004 release, plus cards on the other movies to follow.