Posted By:
Anthony S.Here's a good article from the "Detecting Card Alterations" section (the icon is on the top right of the front page).
http://www.network54.com/Index/86209
Also, if you're collecting T206 commons in fair to good condition, getting one that is slight trimmed (like the Bescher may or may not be) really isn't the end of the world, imo. Hall of Famers, rarities, or SL'ers are a different story.