Hi Doug,
I think you are wise not too fool around with the card. You have a truly unique find. I don't think that the paper residue on the back will limit it's value at all. Experienced collectors will understand that they can do the work with the card themselves if they happen to be lucky enough to win it. If I was an expert in soaking (I'm not
) and wanted this card, I'd rather win it as is and then do the work myself than to take a chance on someone doing the work that's never done it before. Sort of like how they say never to do anything to the finish on an antique piece of furniture if you are not a professional.
In any case, best of luck with the sales, glad to have you on board the forum and hope to see more of your collection in the future!
Steve