B53 SS-21 Dismantlement Final Unit Sept 2011 [coin]

Amarillo, TX: Department of Energy, National Nuclear Security Administration, Pantex, 2011. Presumed First thus. Coin. Very good. Challenge coin/medal has a two-inch diameter. One side has a center image of the American Bald Eagle with the words Pantex NNSA. Around the central image is the following text "Department of Energy LANL * LLNL * SNL * Y12* OST". On the other side has a center image of the B53 bomb and around the central image is the following text "SS-21 Dismantlement Final Unit Sept 2011". From Wikipedia: The Mk/B53 was a high-yield bunker buster thermonuclear weapon developed by the United States during the Cold War. Deployed on Strategic Air Command bombers, the B53, with a yield of 9 megatons, was the most powerful weapon in the U.S. nuclear arsenal after the last B41 nuclear bombs were retired in 1976. The B53 was the basis of the W-53 warhead carried by the Titan II Missile, which was decommissioned in 1987. Fifty B53s were retained during that time as part of the "hedge" portion of the Enduring Stockpile. The last B53 was disassembled on 25 October 2011, a year ahead of schedule. Development of the weapon began in 1955 by Los Alamos National Laboratory, based on the earlier Mk 21 and Mk 46 weapons. In March 1958 the Strategic Air Command issued a request for a new Class C bomb to replace the earlier Mk 41. A revised version of the Mk 46 became the TX-53 in 1959. The Mk 53 entered production in 1962 and was built through June 1965. It entered service aboard B-47 Stratojet, B-52G Stratofortress and B-58 Hustler bomber aircraft in the mid-1960s. From 1968 it was redesignated B53. Some early versions of the bomb were dismantled beginning in 1967. The B53 was also intended to be retired in the 1980s, but 50 units remained in the active stockpile until the deployment of the B61-11 in 1997. At that point the obsolete B53s were slated for immediate disassembly; however, the process of disassembling the units was greatly hampered by safety concerns as well as a lack of resources. In 2010 authorization was given to disassemble the 50 bombs at the Pantex plant in Texas. The process of dismantling the last remaining B53 bomb in the stockpile was completed in 2011. It was intended as a bunker buster weapon, using a surface blast after laydown deployment to transmit a shock wave through the earth to collapse its target. Attacks against the Soviet deep underground leadership shelters in the Chekhov/Sharapovo area south of Moscow envisaged multiple B53/W53 exploding at ground level. It has since been supplanted in such roles by the earth-penetrating B61 Mod 11, a bomb that penetrates the surface to deliver much more of its explosive energy into the ground, and therefore needs a much smaller yield to produce the same effects. The B53 was intended to be retired in the 1980s, but 50 units remained in the active stockpile until the deployment of the B61-11 in 1997. At that point the obsolete B53s were slated for immediate disassembly; however, the process of disassembling the units was greatly hampered by safety concerns and a lack of resources. The last remaining B53 bomb began the disassembly processes on Tuesday, 25 October 2011 at the Energy Department's Pantex Plant.