Acetone won't harm the Coin . I've never used it but many highly recommend it . It has to be a certain way though .
Acetone shouldn't harm the coin. Try swabbing the area with a Q-Tip soaked in acetone. What has me concerned is the "bar" (?) that runs straight across Lincoln's head. It looks like the roofline of a Memorial cent. It wouldn't be the first time that some idiot had nothing better to do than glue two coins together.
Strike through. Looks like a piece of metal, perhaps from another coin, was struck into this coin. Just a guess based upon the photos. Maybe @Fred Weinberg has an opinion?
It looks damaged to me, as if something scraped the surface in different directions and left metal deposits on the outer edge of the area.