Looks like a wheat cent was laying on the dime for many years and left a toning imprint. I don't see any damage.
I do not see any indication of a vise job as the bottom of the "T" in CENT does not depress the rim. I suspect GH#75 has the correct idea. whether stain , corrosion, or pigment I can't tell. IMO, Jim
It's hard to tell from a photo, but yes -if it's flat, it's some kind of stain or transfer. Either way, if the letters are reversed it's most likely PMD. For completeness you should go read the error-ref.com articles on brockage and capped die. But this doesn't have the signs of either of those...
I agree it's either a toning anomaly, or a vise-type damage, but what if it's simply that the toning of the dime was shielded by how the cent sat on it for years. Would it still be considered damage, or just cool toning? I'm assimilating it in the way commemorative distribution envelopes have interrupted toning.
I would say it is just cool toning, unless that tone was actually environmental damage. I agree with the others that it is a very, very interesting instance of toning. It is not an error, but I would most certainly be excited; Not about the monetary value but about the coolness and interesting tale the coin depicts.
Don't get excited as it's damaged. Anytime you see something out of the ordinary ask yourself one question. How did this happen in the minting process?