25th Anniversary Seabees / CB Can Do 1942-1967 Centennial Navy Civil Engineer Corps Silver Medal / Medallion / Challenge Coin
It is 1 5/16 inches in diameter. It weigh approximately .7 Oz (not troy).
There are bronze versions of the coin which are very rare and hard to find. This one is .925 Sterling Silver, tested by Coin and Bullion of Panama City, Florida. The silver version is scarce.