The metal band about 2 1/2" in diameter and 1/2" wide. It's encrusted in a rock type material. It's a bit hard to see in the photos, but, there are numbers 1 to 10 around the band. Some sort of dial? Thermostat? Seems to be made of brass. The outer band has the numbers and is partially attached to an inner band of the same material. I've smacked the "rock" area with a hammer and you can chip off pieces, but, it's pretty tough stuff. Not sandstone or something soft like that. I guess I could be old concrete that's weathered, but, it just seems a bit harder than that too.