Posted By: 
Charlie BarokasPeter,
To elucidate, I think the grading companies are not knowingly holdering trimmed cards, but rather the trimmers have gotten many steps ahead of the conventional halogen light and ruler.  Until someone figures out a better method of ascertaining a trimmed edge from an original edge, all you can do is rest on the experience of the grader.  And I think GAI and SGC are the most experienced.  
Charlie