Marine chronometer Highly accurate mechanical clocks carried on board ships and used for open-water navigation to determine the vessel's position.

Many historic pocket watches and | marine chronometers made by "A. Lange & Söhne" featured an UP-and-DOWN display. Even today, several Lange models are equipped with this very useful function. A special variation of the UP-and-DOWN display was chosen for the 1815 UP and DOWN by Lange. It is based on a patent granted to Otto Lange in 1940 for his method of integrating a | planetary gear train between the movement plates.