Re: Cleaned up that "V" nickel as best as I could ....here's a pic .
I have had coins that were unknown, and heavily crusted, and soaked them in vinegar. After a day, it was still there but when rinsed, it did flake off, and the crust was peacock crystals, and the coins were copper pennies that were under the sand in the ocean. I do know the copper does come out of the coin. In old cobs, which had a tiny bit of copper sometimes, they would very often have a green crust, called Verdigris which I think translates to green grey in Spanish. Sometimes they would have a black silver oxide crust, either way they would clean up fine with diluted muratic acid. As for yours, the palmolive wont make the coin reabsorb the copper. I dont think anything will work. Either leave it like it is, or with a tiny dental pick, and magnifying glass stand, pick each one off. Of very carefully use a knife. If done wrong either will scar it.