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I've found metho and a wood tooth pick useful for removing verdigris from the lettering around a .500 Ag coin also a cotton bud for removing any remaining debris. I've heard there was some criticism about the dye residue from mauve metho. I don't know about the UK but in Australia you can get metho with out any dye. Also useful as stated above for degreasing a coin.

We call it "rubbing alcohol" (not suitable for drinking!) over on this side of the Pond. A decent solvent and one of the choices. I have really come along to liking ammonia with no dyes, etc. for copper nickel or even silver in its alloys and even gold - not that implying this choice is encycopaedic but only amongst the possibilities..

Presumably surgical spirit - being clear - doesn't have any dye problem?

The dye free meths over here is Industrial Methylated Spirit (IMS) and it is widely available. Jerry

A couple of comments, obviously from my perspective (but then again I probably had way too much chemistry, pharmacology, etc.): Pure acetone not generally a problem and not nearly as toxic as many may lead readers to believe. In the States, we get it at Home Depot for about $8 per quart and that is quite a quantity. It will react on long exposure to copper surfaces. I recommend it applied with the aforementioned soaked cotton buds or "Q-tips" as we call them on this side of the Pond. Please do not scrub surfaces, and I suggest tamping the surfaces or worst case very light circular strokes sans pressure applied. The cotton on these buds is sometimes not cotton or is of tight wound fibers that are possibly more likely to damage coin surface. Even after acetone treatment, I wash thoroughly with tap water then apply WITH MY FINGERS and rub into the surface mild dish detergent. I then rinse even more thoroughly and then tamp dry with a high nap white cotton towel. My favorite solvent, and not just for organics, is the aforementioned ammonia which should be without colorizers or additives if possible. I then do soaks for varying period and use the soaked cotton buds to again work the surfaces in like manner to the acetone. This will reduce some oxidants and not damage the metal on silver, gold or copper nickel but can not guarantee copper and would therefore probably not use it on copper... There are also the redox tricks which will pull away generally more problematic surface oxidants. Many ways to do it, and experimentation is suggested on lesser coins. One method is to microwave vinegar for 2-3 minutes and then throw in a thin sheet of aluminium, and then baking soda in modest amounts (such as 5 ml/one teaspoon), and then the coin. This one is more fun than the others but have to take care. This REALLY works well on gold coins with those infernal red copper spot oxidations... Blah, blah, blah,,,,,,Anyway, just a couple of points....