An American two-day marine chronometer Hamilton Watch Company, Lancaster, P. A., circa 1942/3 The circular four pillar single chain fusee nickel finish movement with Harrison's maintaining power, Earnshaw type spring detent escapement and uncut monometallic ovalising balance with cylindrical timing weights and helical balance spring, the engine-turned backplate with mainspring set-up ratchet, balance locking fork and inscribed MODEL 21, 14 JEWELS, HAMILTON WATCH CO., LANCASTER, PENN. to margin, the frontplate with conforming engine-turned decoration and stamped with serial number 2E2960 , the 4 inch circular silvered Arabic numeral dial with subsidiary seconds dial inscribed N 2960, 1941 beneath signature HAMILTON, LANCASTER, P. A., U. S. A. and DOWN/UP state-of-wind dial to centre, secured by a screw-down bezel into a lacquered brass bowl with shuttered winding hole to underside, now mounted via the original gimbals into a later mahogany two-tier box with glazed top panel, brass side handles and simple clasp to front, 19cm (7.5ins) wide excluding handles. At the outbreak of the Second World War there were no domestic makers of marine chronometers in the United States hence the U. S. Navy looked to watch manufacturers to develop timepieces that would be both suitably accurate and able to be mass produced. The Elgin and Hamilton watch companies both rose to the challenge but it was only the latter who were able to satisfactorily fulfil the brief for mass production. In addition to the model 21 chronometer Hamilton also produced a smaller version, the model 22, which was essentially a gimballed deck watch. In use the model 21 proved extremely accurate hence is considered by many as being at the pinnacle of mechanical marine timekeeping.