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MEWheatIt is generally recognized that there are two back variations for T201's; according to Lipsett, the Dougherty/Lord has only been found with a Factory 649 back, resulting in its "scarcity".
I also believe that a number of cards were double printed with each factory number, effectively meaning there were some single printed cards in the set. It is apparent when you look at the edges of cards that were "miscut". T201's had a symmetrical design from left to right and most of the miscut cards have multiple types of miscut edges - except for (presumably) the single printed cards. It appears that there are around 10 single printed cards on a sheet.
I don't have enough information yet to support this line of reasoning but will report in at a later date when I am more certain.
MEWheat