I love the toning on the one you displayed. Of course, you don't want to clean them or do anything else, since it doesn't appear that there is any PVC damage, just plain old sulfur influence from the paper around the coins.
As far as this being artificially toned, it really depends on the standard definition of what is and isn't intentional toning. There are the "shake and bake" doctors who have stunning toning that took a few hours to create. That's artificial toning by anyone's standards, I would say. There are those who leave a coin in the window to acquire toning. Or, as in this case, the coin was in a holder, folder, or envelope and acquired toning. I don't see that as artificial (although if you stretch the definition, you could say it didn't occur without help), and the
TPG's don't generally call that artificial toning, either.
In fact, sending a Bust Half with wonderful bright bullseye toning acquired from an old Raymond holder to PCGS will sometimes get you a little better market grade than the same coin without the "acquired" toning.
At the end of the day, it just depends on what collectors like. I like toning on my type coins, especially my nickel types, as that is hard to find nice, but I hate toning on my commemoratives. All depends on who wants to pay what.