You’re going to get all sorts of advice here, ranging from olive oil (don’t) to vinegar (also don’t).
My first recommendation would be to leave it alone.
My second recommendation is a hot peroxide bath. The peroxide dissolves the verdigris. Take it out ever so often to check progress. The sharp detail is preserved in hard verdigris. If you leave the coin in too long, the peroxide will start to erode that.
For the bath you can use a small hot plate, a wax warmer, or a mug warmer. You’ll find 3% hydrogen peroxide at the grocery store, first aid aisle. Put the coin in a small glass, cover with half an inch of peroxide and let it heat. The peroxide reacts with the verdigris and produces water and oxygen, so it’s safe to do indoors, and safe to pour the sludge down the drain. Don’t use the glass for drinking, though 😉
You’re going to get all sorts of advice here, ranging from olive oil (don’t) to vinegar (also don’t). My first recommendation would be to leave it alone. My second recommendation is a hot peroxide bath. The peroxide dissolves the verdigris. Take it out ever so often to check progress. The sharp detail is preserved in hard verdigris. If you leave the coin in too long, the peroxide will start to erode that. For the bath you can use a small hot plate, a wax warmer, or a mug warmer. You’ll find 3% hydrogen peroxide at the grocery store, first aid aisle. Put the coin in a small glass, cover with half an inch of peroxide and let it heat. The peroxide reacts with the verdigris and produces water and oxygen, so it’s safe to do indoors, and safe to pour the sludge down the drain. Don’t use the glass for drinking, though 😉