A 20th/21st century proof will not stand any kind of intervention, I 100% agree, and have said so endlessly on this forum...it is hoped they can be bought without grime? Earlier proofs? Well, you pay for what you get. You mention Olive Oil, CJ, olive oil is not something to degrease a coin with, which is all I'm talking about. It can soften residue, sure...but you then need to remove it, as it also (eventually) becomes rank and gummy, which is why I no longer use olive oil without removing it afterward! The best thing for removing olive oil? As you say, each to his own, but I think your statement re an acetoned coin meeting a rejection by TPGCs was over the top to say the least!