This denarius has been sleeping in my father-in-law's collection for 40+ years. He bought it in Maestricht, 1972, for 85 Dutch guilders, quite a lot of money in those days. It acquired a patchy patina (or maybe the patina is even older). Should I remove it? And with acetone? The denarius is from Faustina II, with Fortunae Muliebri reverse. That means (both words interpreting as a dative singular): "To the Female Fortune". Apparently an uncommon coin and the only one with this reverse legend. 18 mm, 3.43 gr.
I would certainly attempt a gentle chemical cleaning on that one as it looks like it might turn out to be a gem.
I'd soak that coin in a weak acid (lemon juice or white vinegar), keeping a close eye on it and dabbing it with a cotton swab periodically. Rinse thoroughly afterwards, soak in a weakly alkaline solution (baking soda and water), rinse again, dry.
