Thanks Rhett.  Just one quick follow up.  Where is the best place to look for the tough backs? (My collecting so far has been limited to t205 beaters, so i haven't spent much time looking for t206's with tougher backs 

)
Would i have the best luck on ebay?  Or would I do better looking at the major auction houses?  Or even the BST here?
Thanks so much for all your help.