Nice coin! Just as a note, toned coins aren't really considered a mint error (that I know of). They are a factor of what environment they are stored in, and what chemicals they are exposed to.
Hate when that happens, but it is inevitable in cases where we don't store our coins properly. It even happens when we do store our coins properly. Still, with toned coins being all the rage and such I think you might have the beginnings of something good........
