I've had this card for a couple of years now. I set it to the side to decide whether it should be in my Mariner collection or not. Is it just considered an uncorrected error or is this the way Topps wanted to do it. I present you the 2009 Topps #657 of Aaron Heilman:
The front says Cubs.
The back shows the Mariners.
Aaron was traded in the off season by the Mets as part of the JJ Putz deal. He was sent to the Cubs before Spring Training. He never saw the field for the M's. What do you think, is it a Cub, a Mariner, or both??