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leonTough situation.  I bought a large group of cards that had glue on them too. Some of them (Obaks) I soaked and it came off pretty well. If I had a mint card I would probably not do that. I did have reasonable success at luke warm water and a cue tip and very gently rubbing it.  On a few of them my gentle rubbing became signifiacant paper loss so be careful.  Depending on the card I might even leave well enough alone, especially if it were valuable. Good luck......some others probably have more experience than me.  regards