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Robert SWithout weighing-in on whether a postcard is a card is a card debate...
In addition to the list of Cobb postcards listed by Richard, above, which included the 1907 Dietsche, Wolverine News, Novelty Cutlery and HM Taylor Postcards, is this one, below
It is a 1907 American League Publishing Co. postcard, albeit in pretty tough shape (then again, it's the only one I've ever seen):
The Amer. League Pub. Co is the same Cleveland company that issued the single player cards in 1908, the listing for which is in the SCD big book and on OldCardboard.com.