Very neat cards! I just went out and read George's article on them - here is the link in case anyone is interested.
http://www.oldbaseball.com/refs/Myst...ball_Cards.pdf
You might want to post this in the Ebay/Vintage Card Auctions B/S/T in the B/S/T section, as some folks might not see it in this section.
Seems fairly certain they must have been proofs or prototypes from that time - they almost look a bit like Berk Ross cards to me, although they are probably about three years later than the last set of those cards. I am thiinking that whoever wrote the names on the back must have been involved in the production, somehow - I'm guessing it would have been tough for a collector to get the names correct for all 100 or so football players, otherwise. Would LOVE to find the whole story on these.
Good luck!