How do stamp hinge "stains" affect grade?
 

I have a really nice '52 Bowman Snider that looks at least EX to me, save for what appear to be slightly darker areas on the back that look as if they were caused by stamp hinges. There is no paper loss. I was thinking of sending this in to SGC with some other cards, and was curious as to others' experience with this kind of issue. Thanks for any light you can shed.

Any type of marking like that will certainly hurt the grade, especially with SGC. If I have beautiful card, albeit with some small flaw, I may use PSA instead because of the qualifiers. For example, I'd rather have a PSA 8(St) than and SGC 30.