Right now I have what’s called a fiberglass pencil that seems to be relatively effective in removing it. It seems like short of using chemicals the only way is mechanical
I wouldn't take all the green off. I think it's rather nice. Part of the patina on a very old coin. But that's just me. I collected these a while back.
Good thread, enjoyable on a nice Saturday morning in the hills. Here is mine, 17mm. Antioch?, courtesy @Victor_Clark
This one just arrived, courtesy of @John Anthony : Constantine I, AD 307-337. Roman billon centenionalis, 2.89 g, 19.5 mm, 12 h. Cyzicus, AD 331, 333-34. Obv: CONSTAN-TINOPOLI, mantled bust of Constantinopolis left, wearing pearl-diademed helmet and holding inverted spear. Rev: Victory, standing left on prow, holding spear in right hand and shield in left hand; in exergue, SMKB. Refs: RIC 93; Cohen 21; RCV 16477; LRBC I 1234.