Those are from a series released by the American League Service Bureau. They are actually numbered like baseball cards on the front and quite a comprehensive run starting about 1930 and running through the decade. There are several that also carry photographer stamps on the back like Underwood for example and they usually have a stamp from the AL Bureau on the back but not always. They were released over a long period of time so the style is probably just a change in paper at some point.
Rhys
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