Posted By:
Kevin Saucier"I don't follow... how can the rails, which don't come anywhere near the corner, damage the corner? Are you saying the card is too tight in the slab so the whole card is being crushed?"
A collector and I tried this. We repeatedly hit a vintage thick-layered card against the rails on an open slab. The force caused dents on each side and the cardboard to split, exactly like the card displayed.
Imagine the corner of the card is a zit and the rails are fingers...you get the picture 
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Kevin Saucier