How about a blank Red Lion Inn / Gold Country Elko, slot card? Seriously, it's true. One of the trips they ran out of cards with the airplane on it and they were handing out white cards, no markings, just an ID #, players name and the Mag. strip. Of course everyone would have to take my word for this, and I think the concept or no markings cards, means it could be from anywhere. No real attribution.

If I saved one, it was before the last move (putting my life in storage, going through a flood, and moving what was left into a semi-trailer on higher ground) So I'm not sure if I still have any.

Blank white, six digit number in the lower left, 3/4" from the left edge, with the players name above it.