Unfortunatly, I still cannot scan stuff to put pix on here, but we used to collect all those paper coupons for prizes at Harrah's Reno and Tahoe. They were good for gift shop items and it was the most popular gimmick in the Reno Tahoe area. Still have some coupons since I used to collect everything. Not really the same theme as slot cards as we know them today. The closest thing I have is a "slot" card issued by the Mint when they did not have machines as we see them today with a slot for a card. It was to track your play for comps tho and says "slot" card.....
Think this would have been the first "slot" card since it was given so the player could receive comps and benefits for his amount of play....Mel