In 2013, Valve and the tabletop game company WizKids collaborated to produce an exclusive chess set themed around Team Fortress 2 that was sold on Valve's website and on ThinkGeek. Each copy of the set came with a digital code for a hat called the Grandmaster, where the head piece would change as your killstreak increases. Aside from "Grandmaster" being one of the highest titles awarded to chess players by the International Chess Federation, the hat's item description references a pair of highly publicized chess matches in 1996 and 1997 between former World Chess Champion Garry Kasparov, and IBM's chess-playing computer Deep Blue.