A Complete Guide To Cleaning and Preservation of Coins, p.9
MECHANICAL CLEANING OF COINS: Using a Toothpick
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Most of the Dirt is Gone, Natural Patina Preserved
Now you need to clean the coin with a toothbrush and toothpaste under the running water. The next step is to examine the coin under a magnifying glass and look for any dirt remaining inside the lettering or in other small features of the coin's design.
Dirt Residue Inside Letters on Coin Design
Additional application of a toothpick and then brushing would get the coin cleaning job done.
