The magician says that they will multiply the money of a spectator, but of course, an initial investment is required. The spectator provides a dollar bill (signed) and then it is changed into a lottery slip, so now he is a potential winner of millions of dollars...
As the spectator does not seem very happy with the investment, the magician offers to buy back the lottery slip. He removes a wallet from his back trouser pocket (showing empty hands before) and within it there is a sealed envelope, fully examinable, with the signed note inside.
It's the classic Bill in Wallet effect with a new presentation, and the great difference that the wallet is at the back pocket and not in the inside coat pocket as usual.
It can be used for close-up or stage magic.

Note: A "card to wallet" type of wallet is required.