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warshawlawfront image was used in the second Gehrig card of the 1925-30 postcard back exhibit cards.
I don't think it is a reprint of a W517 because there is no number.
I have seen one specimen (I think it was in a Lipset auction) where images from the PC back boxing and baseball cards were made into a 4 on 1. Since there is only 1 and I did not see the back, I have no idea if it is an exhibit card or some thing else. However, I can cull my old catalogues for it if you like. Judging from the size and the irregular cuts on two borders, I'd guess that a 4 on 1 of some type is the source. The fonts are all wrong for a true exhibit 4 on 1.
A second possibility is that it is a locally manufactured arcade card. Numerous arcades filled their dispensing machines with privately printed cards that often used images from other sets. I have handled a few of these in the boxing and non sports areas.