1927 S Quarter Cleaning

thanks Adam--will leave as is--

Leave it be

In short, no it won't.

"Black" on silver coins is almost always tarnish, or silver sulfide. It is not blobs of a foreign contaminant stuck to the coin's surface, but the metal of the coin's surface itself reacting with sulfur in the environment. The tarnish is a part of the coin now, so there is nothing for the acetone to simply "wash off". You can only "remove" tarnish by "undoing" the chemical reaction - this is what e-z-est or similar "silver dips" do. These dips contain thiourea and sulfuric acid, which rip the silver sulfide away from the coin's surface, leaving clean metal behind. Because some of the silver has been removed from the coin, this is normally regarded as the "bad" kind of cleaning and, in the case of a worn and circulated silver coin like yours, would result in a bland, grey, "washed-out-looking" coin that pretty much everyone would find less appealing than it's current appearance.

The coin, as it stands, does have a little of that "circulation cameo" effect which some people seem to appreciate in their old circulated silver coins. The fact that the high points are mostly free from blackness proves that the colour developed while the coin was in circulation, so it's an honest part of the coin's history. And the contrast certainly helps you see the details on the coin that will otherwise be lost to the eye if all the black stuff is removed.

TLDR: while acetone won't hurt, it won't help either. Silver dip will "help" by removing the tarnish, but you almost certainly won't like the results.