I have been holding on to this card for years, not knowing what it is worth since no one I have asked has ever seen it before. Hopefully someone on this forum has come across it before and can shed some light:

It is 1991 Upper Deck Game Breaker Holograms #GB1 Barry Sanders, but it is an error card, as the back of the card is blank. The background, border, etc are all printed, but there is no text whatsoever, not even the card number. I am assuming it is rather rare since no card shop I took it to could give me a price.

Has anybody out there seen this one before?