The three-bladed radiation warning symbol, as we currently know it, was "doodled" out at the University of California Radiation Laboratory in Berkeley sometime in 1946 by a small group of people. This design is supposed to represent activity radiating from an atom. This trefoil pendant is cast in solid silicon bronze. I thought it only fitting to give it a corroded surface finish enhanced through oxidation. With a diameter of one inch across, it's slightly larger that an ordinary quarter although somewhat thicker.