If you intend selling it, don't do anything with it.
You can take the patina off, but you can't put it back (easily)
it has a green patena on it which isnt bad but i was wondering if it would take away the value.
If you can post pictures I may be interested in buying it from you. I have almost a complete set of Lincoln's and I'm just missing a few, 14 D is one of them.