U S AIR FORCE C-5 GALAXY Challenge Coin. This is a great looking US AIR FORCE C-5 Galaxy challenge coin. Coin has reeded edges and is about 1 9/16" in diameter. All details are raised lettering. Coin is contained in an acrylic air tight holder. The Lockheed C-5 Galaxy is a large military transport aircraft originally designed and built by Lockheed, and now maintained and upgraded by its successor, Lockheed Martin. It provides the United States Air Force (USAF) with a heavy intercontinental-range Strategic airlift capability, one that can carry outsized and oversized loads, including all air-certifiable cargo. The Galaxy has many similarities to the smaller Lockheed C-141 Starlifter and the later Boeing C-17 Globemaster III. The C-5 is among the largest military aircraft in the world.