Wow, cool coinstar find today. I’m wondering if this is silver, because of how the coin aged. Looks like how silver tarnishes.
There was also a James Garfield $1.00 coin in there too. I actually wondered if this dollar coin was some type of token or something. It just seemed so simple of a design, especially the obverse. Did a quick google search and, yeah it's a real US minted dollar coin.
Would acetone be something I could use to dip this coin in to try and gently get some of the debris off of it?
Distilled water first, then let it dry. If there's still visible debris, try acetone. But most of what you see may be toning, and neither water nor acetone will touch that. You'd need to use a chemical dip, and you really don't want to do that -- the coin is more attractive as it is, at least in my opinion.
From the reeding, it looks like the coin hasn't seen too much circulation. It's got debris which you can see along the jawbone and cheek, some in the hair and lower neck areas plus around the numbers and letters. The reverse isn't has bad in regards to raised debris. I've not done anything to it at all. Just wanted to see if there was a way to get some of that debris off of it.