At least that's what I think he looks like on this dime. I'm guessing someone was using a magnifying glass and trying to melt Roosevelt's head.
Get a Fresnel lens out of an old large screen TV. You can develop temperatures of 2000 to 3000 degrees with them at the focal point.
I've got a Fresnel lens that's about 16x20 inches. It will melt silver and zinc. It might soften copper at noon on a cloudless day, but I've never succeeded. It won't do much more than discolor a clad coin. A bigger lens will gather more light/head, but it'll also focus it into a larger spot -- the size of the spot is proportional to the lens' focal length, but that focal length is usually proportional to the lens' width. My lens focuses to a point larger than the blob on that dime. I suspect a small torch. Radio Shack used to sell a torch that used one cylinder of butane and one cylinder of nitrous oxide, and claimed temperatures up to 5000 degrees F. That thing would melt anything, as long as it was small enough not to carry away the heat too quickly.
