In autumn the tools for 13½ line chronograph were produced. This movement is to replace the 13.33 which has
become too costly, as weel as the 13 and 15 line chronograph movements bought from the Valjoux factory.
In 1913, Longines produced a calibre for a chronograph-counter intended for use in wrist-watches. This movement was manufactured and sold, despite some modifications in its construction, until the technical office, which was aware of the potential demand from the market for timing devices, started working on a chronograph that would replace it. The 13ZN, whose development started in 1936, was built to replace the 13.33Z first made in 1913.
In 1936 the equipment has been expanded to include tools for the 13ZN chronograph with a semi-instantaneius counter which will
be a good replacement for our old 13.33 chronograph. The tools for making all the steel parts have been made at the Longines factory.
This movement is coming at the right time, because wrist chronographs are the height of fashion and few companies have an original chronograph calibre.
With a diameter of 29.80 mm, the 13ZN chronograph had a semi-instantaneous minute-counter. It was made in a version with one push-piece and another version with two push-pieces.
At the end of the year, some new articles were examined with the agents conference in January 1938 in mind; they are: a 12.68z watch with a centre chronograph seconds, a 17 line watch with a centre seconds a special enlarged dial for use in aviation, and finally, a cased 13ZN chronograph with water-resistant push-pieces. Patents will be applied for in Switzerland for all three creations.
Once the model was in production, attempts were made to exploit the 13ZN more fully, for example by fitting it in a water-resistant case specially developed for that mode. This calibre also served to create a chronometer, based on the 13ZN without the chronograph mechanism. During the Second World War, Longines produced a version of the 13ZN with a dragging hour-counter, however. Positioned at 3 oçlock on the dial, this device complemented the centre minute-counter.
Wrist chronographs with hour-counters have also been delivered. Unlike the other models with hour-counters which have 3 eccentric dials, the Longines model has only 2 eccentric dials since the minute-counter hand is fitted in the centre.
Created to replace the 13.33Z, the 13ZN was intended for wrist-watches that would meet the considerable demand for chronographs which characterised the war years. Documents in the Longines archives indicate, however, that it was brought into question before the end of the war, probably because the production costs were too high in the opinion of the technical management at Longines, which was keen to reduce production costs for all the company’s calibres. In 1947, the St. Imier factory thus developed another chronograph calibre for wrist-watches.
We could try to develop a wrist chronograph that is cheaper to produce than the current 13ZN.