During World War II, Hamilton stopped production of watches for consumers to concentrate on the huge task of providing the forces with a total of one million timepieces.

The Hamilton marine chronometers developed in the 1940s were the first to be created by modern manufacturing. Chronometers were vital naval equipment for calculating longitude and plotting location and direction and were used by the US Navy as an alternative to radio to find position. They represented vital military equipment, since radio time signals could be intercepted and falsified by the enemy.

During the course of the war Hamilton produced 10,902 marine chronometers that met the toughest demands for accuracy and reliability, as the only company with the capability to provide this support, managing to develop and produce these in a little over a year. The company’s efforts were rewarded in 1943 with a US Army-Navy “E” Award, presented for excellence in production of military equipment.