I collect old vintage coins from many places. They are all from foreign countries (I live in the USA) and typically date anywhere from the 1940s to the 1980s. I have a few that date all the way back to the 1700s, but I'm not drilling holes in anything that old. As you can see they are grubby and dirty. A good soaking in dish detergent with a gentle scrubbing using a soft toothbrush still doesn't remove all the grime.
It's time to get my gloves on and get down to business. Using my magic coin-cleaning formula, I get the things pretty darn clean.