Naval Security Group Activity. Surface / Air / Submarine. Condition : Used, and in good shape. This coin is 1 3/4 inches in diameter. Never personally given any of the coins. All coins are guaranteed to be in excellent condition unless otherwise specified above. The free listing tool. The item “Naval Security Group Activity San Diego Chief’s Navy Challenge Coin / SEAL / NSA” is in sale since Thursday, October 23, 2014. 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.