longitude by chronometer, with an accuracy better than 1 second a month. Thirty-six watch and clock companies applied. Omega's entry used a calibre 1525 movement giving an accuracy of less than 5 seconds per year and was selected after a year of testing at sea by the French Navy Hydrographic and Oceanographic service. With the Omega Marine Chronometer wristwatch movement of 1974 as a basis a Quartz Marine Chronometer clock movement was designed with a high-frequency 4.19 MHz (222 or 4,194,304 Hz) quartz oscillator that should be capable of an accuracy of approximately ± 0.01 second/day. Where quartz elements were usually lens-shaped, this one was barrel shaped. It had very low ageing properties, a low thermic coefficient, and was able to function between -10 and +60˚C. The timepiece was tested by the Neuchatel Observatory under rigorous conditions: temperature variations, thermal shocks, magnetic and electric fields, mechanical vibrations etc., which after 47 days of examination earned it the official quartz "Quartz Marine Chronometer" certificate. This is a higher standard than the Marine Chronometer (mechanical) by which standards the 1974 wrist Chronometer was tested. The ships clock featured an external electronic connection “1Hz – 1 V”, an electronic switch to stop the movement or operate at normal or double rate (the second hand advancing in ½ second increments for optimal timing of celestial objects angle measurements) with a locking knob to prevent accidental actions, power reserve switch with power indicator to check the battery condition, and a frequency regulator. The clock came commercially on the market in 1980 as the Omega Megaquartz Marine Chronometer at great expense, but was predominantly used for military application with the French Navy, who used the Marine Chronometer clock in the majority of their fleet. By that time, bearings could be taken by means of satellite navigation. Nevertheless, French Navy regulations still required an independently operated timepiece on board so that, in combination with a sextant, the ship’s position could be determined by celestial navigation. The Marine version (ref. PE 5801) has extra shielding against radiation, the versions for the Public (PE 5802 and PE 5806) do not have this extra protection. At the time of production, this was the most precise portable autonomous timepiece, second only to an atomic clock. The ships clock was supplied accompanied by an official "Quartz Marine Chronometer" certificate in a sturdy mahogany box with brass fitting and was very much a