1989 Upper Deck Baseball Forum

In the 89 Upper Deck baseball set, card number 117 Gary Pettis. In the picture on the front of the card he is holding a card in his hand. It looks like the back of this card but is missing his bio information. What card is he holding?

It looks like the card he is holding is missing the hologram too.  My guess is it was a form of prototype of the card that was never released, but it is just a guess.

Here's an old blog post discussing that card, with similar ones noted in the comments:

http://uglybaseballcard.blogspot.com/2008/02/cards-thing.html