To beat Archie to the gun....
John, they can be redeemed at the casino where they were originally issued. For example: Hilton bought Bally's Grand who bought Golden Nugget, therefore Golden Nugget and Bally's Grand (renamed The Grand) chips are redeemable at Hilton. Claridge and Wild, Wild West (was always a part of Bally's) can be redeemed at Bally's. Additional places for redemption: Caesar's Boardwalk Regency - Caesar's; Harrah's at Trump Plaza - Trump Plaza; Trump Castle - Trump Marina (This was just a name change); Trump World's Fair - Trump Plaza. Exceptions are: Playboy, Atlantis, Brighton and Sands do not have a currently open casino that purchased their operations so one would have to go the State of New Jersey for redemption. The State maintains a pot of money deposited to cover all unredeemed chips at the time those casinos closed.
Archie, did I miss anything? Chuck