11/16” with mark on reverse by maker “W&H Co.” After the surrender of Japan and the end of WWII as the project wound down, each of the approximately 132,000 project members received one of these pins. The scarcer version in sterling was given to those who served longer than one year. Pin is .75” in dia. Project participants ranged across the country from areas such as Columbia University to Clinton Engineering Works in Oak Ridge, Tennessee to New Mexico. Historic, scarce and essentially Mint. Our last exceeded $275.00.