A H.S. experiment using mercury to change the color. BTW Mercury not something that you want to handle .
My older brother and I coated Merc. dimes with mercury from a broken thermometer when we were Kids. Wer,e both still alive, but a little deranged.
Plated. Watch the TV coin shows. They're always plating state quarters and other coins with gold. And yes, they are worthless junk other than the face value.
