I've always found that the acetone evaporates from the surface so fast that it leaves a smear at its periphery. Hard to explain but if you put a small drop (only as an example) onto the field of the coin, it (I'm guessing) forces any surface residue/grease to the periphery of the acetone 'bead' and then quickly evaporates to leave a circular ring/smear in its place. Of course, putting a flood of it on the coin replicates this to a greater degree, at least in my experience.
i genuinely salute you if you can pull it off, I'd love to be able to. I've long since given up with decontaminating high-mirror proofs, preferring to leave them to someone else, you perhaps?
no, I have one very strict rule with mirror proofs, and that is I have to like them as they are, or walk on.
don't get me wrong, I'm brave enough to play around with anything currency, and always do, even with hammered. Though with hammered it's generally nothing other than an exercise which says 'I love you, coin'!