There's issues with the square cornered ones. I can't remember the specifics, but depending on the paperstock, it may be fake(or at the very least presumed fake by many in the hobby).. Just take a look through the old threads. This was one of the better threads in the pre-war section.
http://net54baseball.com/showthread....d+bread+square
Personally, I only own one of these. Jackie. Square cornered, white thinner stock..I still don't know if it's real or not. I don't have much into it either, so I've never really concerned myself much with it..