Wikpedia had this information: Celebrity Poker Showdown was a celebrity game show on the cable network Bravo. It was a limited-run series in which celebrities played poker, and ran eight tournaments during its five-season run.

In each show, five celebrities played a no limit Texas Hold 'em tournament for charity. The winners of each qualifying game won a silver commemorative poker chip and advanced to the championship game. The winner of the championship game won the grand prize for his or her charity as well as a gold commemorative poker chip. Each tournament featured 25 celebrities and consisted of six episodes, five qualifying games and one championship game.

The TV series was produced from the Palms Casino in Paradise, NV, from Dec. 3, 2003 to July 5, 2006, before being changed to Harrah's in New Orleans, LA for the championship game.

I guess the chip was a promotional item given to those who were there for the taping session or live shows that were broadcast over Bravo cable.
For more information about the production go to: http://en.wikipedia.org/wiki/Celebrity_Poker