From the great Ray Piatt, who made so many cool (and high quality) mentalism props in the 1970's through 1990's.
This innovative design and method for a peek wallet is probably from the late 1970's or early 1980's. Leather wallet, which snaps securely closed with an outer strap.
It is a practical method, using a wallet you can use everyday, but when a spectator writes a message on the back of a business card, and slips it into the wallets inside pocket, you can get a clean peek at the info as the wallet is closed and secured with the snap strap.
Original Ray Piatt leather wallet and instruction sheet. (You will probably want to change some of the "propping" that has been put into the wallet, but this is easily done with some scissors and glue. And is not really necessary to do if you don't want to...)
Very tough item to find now, and a great addition to your collection and/or performing repertoire.