Naval Special Warfare Center Navy SEAL Training. The coin is 1 5/8 inches in diameter and made with hard backed enamel. It has a serrated edge. NOTE: Never personally given any of the coins. All coins are guaranteed to be in excellent condition unless specified above. The free listing tool. The item “Naval Special Warfare Center SEAL BUDS Class #307 Navy Challenge Coin / Forces” is in sale since Wednesday, December 06, 2017. This item is in the category “Collectibles\Militaria\Current Militaria (2001-Now)\Original Items\Challenge Coins”. The seller is “rolyat11″ and is located in Panama City, Florida. This item can be shipped worldwide.