Help with Goodwin Cobb Blank Back

[z28jd]

I don't follow blank backs close enough to know if more than one exists of any non-SL card, but I will say that it shouldn't be impossible. We know cards were printed multiple times on the same sheet and you would have to assume if someone is keeping a scrap card, they were more likely to save a Cobb than some common player. Two could exist just from going to the same person off the same sheet. Also, the cut/size of a card shouldn't matter since they weren't necessarily factory cut. That being said, I don't trust blank backs unless I've seen them in person or someone I trust a lot.