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T206Collector...and speak with a clerk. There are certain kinds of erasers out there that do not overly disturb the paper. I believe they are the gray gummy ones. Stay away from the hard pink ones, like on the backs of pencils. Those do more damage to paper. I would practice on pencil marks on your own first before putting eraser to card.
My PSA 4 (MK) T206 Chance was crossed over into an SGC 40/3 holder with an erasure on the back. In addition, I have an SGC 40 southern leaguer with an erasure on the back. I think the SGC rule is nothing higher than a VG is possible with an erasure.
Here's some ideas:
http://www.dickblick.com/categories/erasers/#charcoalerasers
This one sounds particularly good (but I've never used it):
http://www.dickblick.com/zz210/08/