English: Omega Constellation Megaquartz F4.19mhz ships clock, French Navy issued. The calibre 1525 movement uses an advanced 4.19 MHz quartz resonator operated at 2 ²² or 4,194,304 Hz frequency giving an accuracy of less than ± 5 seconds per year. The clock was designed at the request of the French Navy. This ships clock was available commercially 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. The clock was supplied in a mahogany box with brass fitting and was very much a case of function over form and built to the highest of military specifications including anti magnetic shielding. The clocks were all individually numbered on a brass plaque and ran on two standard AA type batteries. The battery condition can be checked and when changing the batteries they can be exchanged one by one to keep the time running. A set of batteries provided power for circa 2 to 3 years. The second hand can advance in ½ second increments for optimal timing of celestial objects angle measurements used in celestial navigation.