At our house we have a wood kitchen-top. We had placed on it a tin can (a typical cookies can), and probably because of some water sitting there, a black ring has been formed where the tin touched the wood. However, the tin does not show any signs of rust.
The kitchen-top appears to be made of hardwood pieces glued together, and only on the top and sides there is some kind of finishing, which has worn off at some places.
The main question is how to remove the ring. Some questions to which the answers would help are also: what is the stain exactly? how can we tell what finishing it has? can I sand it and patch it locally?
The whitening near the ring has been created by using household cleaning material because initially we thought it was rust sitting on top of the wood. We also thought it was a water stain and tried the iron-and-cloth solution, but that didn't work either.
I would like to avoid sanding the whole bench for the hassle that involves as well as the fact that I don't think I'm qualified for that.
Some images:
full ring:

partial close up:

