Barbed wire encircled this double-compartment storage building and a 24-hour sentry kept armed guard. The top secret Norden bombsight, a mechanical analog computer, was accessed through bank vault doors, removed carefully for training missions, and returned under armed guard. The 50-pound instrument was used to determine the exact moment a bomb should be released. The bombsight contained 2,000 precision parts. Its accuracy depended upon the bombardier’s ability to correctly calculate speed, altitude, temperature, barometric pressure, and the “bomb curve.” Setting the instrument required such precision that one reporter likened it to playing a violin. Wearing silk gloves so that his fingers wouldn’t stick to the metal and breathing pure oxygen in temperatures reaching 40 degrees below zero, the bombardier crouched in the Plexiglas nose of the aircraft, the worst seat in the house. This is the only identifiable Norden bombsight building still standing in the United States.