Two Puzzles by Micah Lexier consists of a pair of jigsaw puzzles, each with the die-cut pattern of the other puzzle printed on it. From Lexier's Instagram:
They look like two of the exact same puzzles, but are in fact different. One is the image of the nine-piece puzzle foil-stamped on to the 16-piece die-cut puzzle and the other is the image of the 16-piece puzzle foil-stamped on to the nine piece die-cut puzzle.
The puzzles are for sale in a limited edition of 100 at Paul + Wendy Projects. (via @kellianderson)
Update: See also Jigsaw Jigsaw, the puzzle for fans of the Droste effect. (via @christopherjobs)