Spade Card Monte by Adair.
Performer displays 2 red jumbo spot cards, with an Ace of Spades between them. A spectator is asked to point to the odd card. He points to the center card, which is placed aside. The other two cards are turned over and are seen to be the two red spot cards. But when the face down card is turned over, it is seen to be blank! Performer snaps his fingers, and the blank card drops open to a double card, with a picture of a (gardening) Spade.
We supply all the required Jumbo Cards and detailed illustrated instructions.
Spade Card Monte by Adair