I'm transferring an old Mercury dime collection from an ancient Whitman folder to a Dansco album. Nearly all of the coins show toning characteristic of being locked away in bronze-age folders. Below are pics of one of the better examples--a mix of color and muddy tarnish.
Toning not nice in this case, but can't do much about it, unfortunately. If it hasn't had an acetone bath, at least do that much, but don't expect to see any improvement in eye appeal. It's just that if there is any organic junk on the coin, it should be removed anyway.
The collection I'm moving to the Dansco is kind of funky--as the pics show. Nearly all the coins are AG to G in condition. Those from the late 30s through 40s range a little better. I plan to keep these as-is. Makes for an interesting set, not a lot of $$$ involved.
the Whitman gunk comes off usually. Sometimes water is sufficient in my experience. Most of my collection was in them and have a black ring on the edge and a black/blue back. Its horrible. Look up how to clean stuff if you don't already know, if you want to bother. It gets tedious in a hurry. I don't blame them, they probably didn't have a clue how to design them to last for 100 years back then, but that closed back idea was no good.