This USN Gunner’s Mate – Green House V2 Challenge Coin. This is an original V2 Challange Coin, serial number (#281/521) is a perfect addition to any collection. The coin is 4.5 inches in size, making it a great display piece for any enthusiast. The coin includes an original piece of Bldg. 521 DNA (glass) from the “Greenhouse”. This is a perfect Holiday gift for the person on your list who has “everything” but not this!