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Longines Chronometer, Cal. 15.68z

CHF 3,500


Extremely rare and well-preserved fine LONGINES Observatory Competition chronometer SN. 6708458, Cal. 15.68z, 33 mm (Breguet overcoil hairspring, Guillaume gold screw compensation balance beating at 18000 bph). Aluminium case size is 40mm. Made in 1940s for Observatory Competitions, this movement SN. 6708458 submitted for the trial in 1948 to the Neuchatel Observatory (in wristwatches category!), where achieved a good results (N-Score: 15.20), thanks to Longines precision timer “regleur” Robert Chopard, who spent months of fine adjustments. More information about this amazing movement you could find in the great article, written by Tony C. on Omega forum.

Case: three-body aluminium glazed case, transparent back. Dial: mate silvered with Arabic numerals, black minutes track auxiliary seconds, blued steel baton hands. Movement: cal. 15,68z, nickel-plated, Guillaume gold screw compensation balance, blued Breguet overcoil hairspring, 18000 bph, movement diameter 33mm. Dial and movement signed.

Competition chronometer-quality wristwatch movements are not “ordinary” C.O.S.C. certified movements. These movements were designed and finished to excel in the rigorous world of Observatory Competitions, as conducted in Geneve and Neuchatel in the years 1944 through 1967.

Up until 1967, the exact length of a second was determined by the Earth’s motion around the sun, and the Neuchatel observatory’s precise optics allowed the fine measurements necessary for precise timesetting to be made. Because of this, Neuchatel began to host observatory chronometer trials – a series of the most stringent, thorough accuracy tests in the history of mechanical watchmaking. The trials, held over a period of forty-five days, encompassed ten separate movement timekeeping tests in five different positions and two temperatures. These observatory trials quickly outgrew their roots as a simple certification test, and before long the trials at Neuchatel were a competitive battleground for the finest watchmakers in Europe. Names like Longines, Zenith, Peseux, Omega and many more traded records for decades, fighting to produce the most accurate movement possible. These movements were never intended for regular use, and bore little to no resemblance to what these companies offered their consumers. Along with the technical prowess of the watchmakers building the movements, in the “racing team” there were specialists, the “regleurs de precision”, who worked tweaking a number of movements until they could find a few of them to bring to the Observatory Competitions. By means of fine adjustments, replacement of key parts, use of special lubricants, they could create a few movements for the Competitions. And often they were the same movements for many years.

Watch is in overall great 8/10 condition, running and ready to use!


Brand Longines
Model Observatory Competition Chronometer
Year 1948
Movement Hand-winding
Calibre Lognines 15.68z
Case material Steel & Aluminium
Case size Diameter is 40 mm, Movement is 33 mm
Features chronometer
Box/Papers n/a


In fully working order, still extremely accurate. Very good 8/10 condition, minor surface scratches, scuffs and discolorations through the age. See photos.

Watches are sold as-is, and there is no guarantee of to be waterproof or movement accuracy, due to the nature of vintage watches. Please view all the pictures carefully as they form an integral part of the description. Any defects not mentioned but visible in the pictures will be considered as described.


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