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PaulPaulPaulIt sounds like you are looking at two distinct, but related issues. The 8.75 x 11 pictures are M101-1 Sporting News pictures. The 10 x 13 (or a little smaller) pictures are National Copperplate. The National Copperplates were issued about a year earlier than the Sporting News pictures. There is some overlap in players in the two sets, but not complete overlap.
The easiest way to tell the difference is that the Sporting News pictures actually say "The Sporting News" at the top, while the National Copperplates don't. I believe (but I'm not sure) that some of the Sporting News pictures actually have a credit in the photo to National Copperplate -- so don't rely on that as the distinguishing characteristic.
I just noticed the Standard catalog lists the Sporting News pictures as being 10 x 13. This is a mistake that hopefully they'll fix soon.