Gambling chips were a temporary form of currency used for gambling in casinos.
History[]
In the Toyroom, gambling chips were used in a game of cards between Gaylord Lefevre and the Celestial Toymaker, despite the Toymaker having no need of money. (COMIC: The Greatest Gamble [+]John Peel, DWM backup comic stories (Marvel Comics, 1981). Page 41.)
In 1963, the Twelfth Doctor won eight hundred thousand dollars' worth of chips on a craps table in the Sands Hotel. (COMIC: Gangland)