Mechanical movements and chronometry

From the Longines website: On the right hand side of this page below are links to more history of the brand. Great reading!

In 1952, Longines brought out its first self-winding calibre designed in house, the 19A. The factory was acquiring knowledge relating to automatic winding technology. In 1956, this experience was mobilised for the design of a small oval self-winding movement which was intended for ladies’ watches, the 14.17. Dependent upon the decisive progress made with regard to lubrication, this calibre was fitted with a balance and spring assembly oscillating at a frequency of 19,800 vibrations per hour; it constituted the only self-winding movement for ladies’ watches developed by Longines. The increase in the frequency of oscillation of its regulating organ marked a basic trend in the development of the mechanical movement, particularly in the context of the emergence of technological competition based on electronics and quartz. This progression, rendered possible by the independent development of the components, also had an impact on chronometry. In 1959, Longines developed a calibre specifically designed for observatory competitions. Designated by reference number 360, this movement, rectangular in shape with rounded corners, was produced in a very small series. It was exclusively allocated to the precision competitions in which the major watchmaking companies so eagerly participated. The construction characteristics of the 360 reflected its function: although its total surface area was very close to the limits specified by the observatories, the large size of this calibre permitted the use of a large barrel mainspring and promoted good management of the distribution of energy. In addition, the dimensions of the 360 made it possible to use a large balance and spring assembly oscillating at a frequency of 36,000 vibrations per hour, enabling a very precise rate. The 360 calibre set new records for precision in the wrist chronometer category at the Neuchâtel Observatory.

http://www.longines.com/brand/history/mechanical-movements-and-chronometry