Printed on 1991 Topps Traded “white” stock, these recently discovered dual-front test issues differ from their pack-issued counterparts by minor design and cropping variations.
Make sure to check out this in-depth discussion with comparison pics on the Net54 Baseball forums.
Junk Wax Gems 
I have approximately 22 of these, including the reverse of each player (glossy/matte & matte/glossy). There must be more than one sheet that was made because I have the same dual sided cards that are pictured above and in the forum. I have no doubt that these were test proofs based on the cropping and banner color variations. In fact, some of the cropping changes were obvious and necessary improvements to the final version. The most intriguing card from the bunch that I have is Tom Candiotti/Jeff Gray. – The test card shows the backside of Candiotti’s baseball glove breaking the top red border but with cropped out glove laces. You can also see a slight gap where the glove touches the top border. In the final version, Candiotti’s glove does not touch the top border and the glove laces are clearly visible. Although just a test card, I think it’s much cooler than the Mark Whiten error.
Great stuff! I’d love to see scans if you have any jacksoncoupage@yahoo.com
Happy to credit them to you too if I can use them for an update to this article.