These special measuring tools produced by Greenfield Tap & Die Corporation in Greenfield, Massachusetts, accurately sized holes and threads which were held to close tolerances to achieve interchangeability. Their quality, which could measure a piece of machinery as a “go” or “no-go” machine component, gave America a distinct advantage in World War II (1939-1945). Greenfield industrial workers were so essential to the war effort that they were deferred from the draft, and the town was protected by an anti- aircraft battery, able to shoot down German bombers.