Do you think its possible that the coin was placed in the 2x2 after being removed from a PVC Flip? My understanding is that PVC is (was) used in plastic as a softener. In in the late 50's or 60's, folks were concerned that stiff, hard plastic would ultimately scratch the surface of their coins so manufacturers responded by producing pliable and soft 2x2 flips. PVC was the softening agent and it wasn't discovered until years later that the PVC was actually damaging the coins. I've never heard of PVC in a cardboard 2x2.
More than likely the coin has been oiled with a product like Coin Care, which is nothing more than napthenic mineral oil and an odorant. Oils are insoluble in acetone, the best way to remove oil is with xylene. Oil is completely soluble in xylene.
There may have been some 40 to 50 years ago or more. If you have a coin in a 2X2 that shows PVC contamination it almost certainly was on the coin before it went into the 2X2. Most likely the oil was from Coin Care or something like that, and if it feels oily or sticky it is because too much was applied and the excess was not removed.
It's common to use olive oil to clean ancient coins. As for coins 200 years old, it was probably added to enhance the details and make the coin look better than it actually is.
