Maybe a rim burr, maybe a shaving on the upsetting mill. What concerns me more though is the fingerprint stripes that are gonna develop like a zebra if it's left in a 2x2 just as it is.
I think the 'go to' product for removing fingerprints/oils is acetone, if I'm not mistaken. ie. fingernail polish remover (without any additives). Just don't smoke while using it.
Fingernail polish remover is acetone but it has other additives and if used on any type of coin it will harm the coin. If acetone is used it needs to be an industrial grade.
Hmm, after researching I don't believe I took @Collecting Nut's advice seriously enough. It seems that the acetone in fingernail polish is known to be diluted in many cases. Not sure what they dilute it with but I'm not convinced they would always list that ingredient. I would follow his advice and get an industrial grade acetone just to be sure.
Acetone shouldn't be used on copper where natural light, water, water vapor or even high humidity is present either. When copper and acetone come into contact when there is moisture and natural lighting they react photochemically forming acetic acid. The acetic acid then goes on to further react with copper forming copper acetate. Isopropanol has no such reaction with copper and is recommended as an organic degreaser for alloys with high copper concentration. Acetone is however completely safe to use on silver, gold and platinum. And my wife said I'd never use my lab degrees in real world situations, lol
Generally the nail polish remover has something in it that tastes horrible and a perfume that smells better than pure acetone does. I wouldn't say it's diluted (like with water) but there are additives and it's not pure.
Bleah. I recall now the reason I hated my college chemistry class. I wonder what you could use to remove fingerprint oils with, instead.
Isopropanol is what we use on the copper slide trays to remove organic oils like fingerprints. It's completely safe to use on copper. You gotta make sure you remove the acetone completely if you use it on copper or it will pit the surface and form a blue/green oxidation layer.