Dick Gilkeson noted the line differences on the Williams card and several other cards in the 56 set in his variations publication some time back, 85 to 95 . And with ebay, the number of known cards with these lines has proliferated. I wonder if you looked long enough whether you could find them on all cards in the set.
I have a couple of examples in my set but Darren's prior thread convinced me it would drive me crazy trying to run down all the possible differences on just the Williams, let alone all the other cards in the set
Here are other 56 odditiies