We did the "mercury thing" a lot back in the 1950's; if I remember correctly, it would take on a "hazy" appearance after a period of time. This coin just looks plated.
True, but the last time I had seen mercury was in my great grandmother's thermometer. I did hold a bottle of Mercury once in my science class, right before they had to dispose of it for a school inspection. Stuff was heavy!
I had one just like this. I thought I had something until my daughter told me she painted it with silver nail polish.