I'm not really a room key collector but I just discovered a different variation of a Harrah's AC room key that wasn't on the ChipGuide and thought it might be of interest. It's the white UNLOCK THE FUN key. The previously listed card had the insert arrow at the TOP of the card and the manufacturer's mark was C-00266583N. The new found card has the insert arrow at the BOTTOM of the card and the manufacturer's number is C-00266583O (letter 'O' at the end).