1999 D Dime "Toned" Error?

I agree that it looks pretty cool. Toning of course is a process that occurs after the coin leaves the mint, so there is no such thing as a toning error. Toning can be either natural or artificial. Some collectors will pay a little more for attractive natural toning. Very few will pay more for artificial toning and most would agree that it detracts from the value. Since this coin is only 18 or so years old, I'm thinking that the toning was either applied on purpose or accidentally due to exposure to heat or a chemical or both. Certainly save it if you want, but I think that it is only worth face value.

Always try to add a picture of the whole coin along with your close ups - easier to tell whats actually going on like natural toned or artificial toned.