As an aside, glue back in that era was either water-soluble or not, but even the water-soluble stuff is sometimes so difficult to remove that it isn't worth it (perhaps there was something more than water in some mixtures).
But the non-water soluble glue is impossible - I've never seen cards come off cleanly when removed by collectors. Kudos to Scott for his innovative attempts - I'm guessing one of his remote ancestors collected the data to teach us about various poisonous plants, having fortunately reproduced earlier.
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