Posted By:
runscott...and that's much better than being jaded and cynical like me 
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however, this is a fake. The major clues are in the description, which I won't repeat, but you can also tell from the scan. If this were a real Plank, it would not be glued in a 1945 football guide - even in 1945 this card was recognized as rare, but read on and you will see why this "card" evidently was glued into the book much more recently. Even if we assume the original owner was oblivious to the value, you can look at the facing page and see that there is no impression of the card. If you were to glue a card to a book, you would see some evidence of it on the facing page - indentations, color change, etc.
Finally, the acidity in the paper that this cheap football guide was printed on, typical of ww-II war-time printing (see browning of pages), would have had some effect on the near-perfectly white borders of the reprinted Plank. ...and the cross-hatch marks in the blue background should arouse suspicion (often happens with scanner interpretation of solid colors) as should the bends and missing piece from the left border - you would expect some stains, marks, border discoloration to go along with all the other damage.
addendum - don't be fooled because a card measures correctly and looks real. If you scan a card or a picture of a card, then glue it to cardboard, the resulting scan will almost always look real, and getting it to measure correctly is no big deal.