An effect from Sandy, remastered by Yves Doumergue
A playing card is freely selected (no force of any kind). The magician states that he'd like to mark the card for later identification on both sides, so the spectator signs the front and he places a red spot sticker on the back. The card is then lost in the pack and the deck is tabled.
The magician sets the pack down, snaps his fingers and shows his hands empty before removing a card from his pocket, which he says is the selection...but there's no sticker on the back. No problem, with a wave of the card a green sticker visibly materializes on the back of the card! Oops, it's supposed to be a red sticker. Again no problem, with another wave of the card the sticker visibly turns from green to red (this looks great)! The card is then turned over and there on the face of the card is the spectator's signature.
Comes complete with the necessary Bicycle cards and detailed instructions.