History of Chronometers Pt. 3: Enter COSC

As the ‘60s drew to a close and gave way to the early 1970s, the traditional Swiss industry was erupting into full-blown crisis. While the waking giant of Seiko might have set the old players off balance, the advent of affordable quartz watches threatened to shake the whole system to the ground. The old observatory trials at Neuchatel and Geneva, once vital not just to industry pride but to accurate navigation as well, suddenly seemed quaint and obsolete. If the finest mechanical movement, slaved over for years by master watchmakers, could be humiliated by a simple battery-powered piece, what was the point?

continued from part 1 and part 2.

The death of the observatory trials left a major power vacuum, however. In the early ‘70s, quartz technology was still in its infancy, and the vast majority of consumer watches were still mechanically powered. The buying public was still hungry for accurate movements, but without a regulating body there was little consensus on what “accurate” really meant. To bring order and to re-establish a chronometer standard, representatives from the Swiss observatories, the Federation of the Swiss Watch Industry, and the five watchmaking cantons of Bern, Geneva, Neuchatel, Solothurn, and Vaud joined forces in 1973 to create a new non-profit organization. This organization, the Contrôle Officiel Suisse des Chronomètres or COSC, had a singular purpose—create a standard and certify Swiss chronometer movements.


COSC-LogoThe standard the COSC developed was stringent, a demanding regimen of tests nearly on par with the grueling Neuchatel trials. Encompassing 16 consecutive days of testing, the COSC’s method winds and measures the movement once every 24 hours. Over the course of these 16 days, each candidate watch is tested in five different positions and at temperatures ranging from eight degrees Celsius (46.4 degrees Fahrenheit) to 38 degrees Celsius (100.4 degrees Fahrenheit). During these tests, the watch must remain accurate to within -4/+6 seconds a day on average with a maximum allowed rate variation of seven seconds a day between test days. Five other criteria are also judged, creating a standard so strict only three percent of annual Swiss watch production (a figure slightly over 1,000,000) qualifies for the chronometer label.

Perhaps unsurprisingly, the annual roster of certified chronometer movements is dominated by the largest manufacturer, Rolex. Rolex’s COSC output is so immense that two out of the organizations three facilities (the centers at Biel and Saint-Imier) are almost entirely dedicated to certifying Rolex movements, particularly the Cal. 3135 and derivatives. Meanwhile, the final facility at Le Locle handles the rest of the Swiss industry led by Omega, Breitling, TAG Heuer, and Panerai.

With a roster so overrun by the major players, many have questioned the real effectiveness of the COSC as a real certifying body, claiming that in recent years the organization has become a marketing gimmick for large luxury brands. To help combat this image, in 2009 the COSC worked to establish an ISO standard for mechanical chronometers beyond Swiss production, known as ISO 3159. In addition, the COSC is currently lobbying for the creation of an ISO standard for quartz chronometers as well.

Over the last 240 years, the role of chronometers may have evolved from vital navigation tools to one of the highest expressions of fine movement-making, but one thing has remained constant. Through it all, they’ve been at the forefront of mechanical innovation, and an undeniable part of what makes horology great.

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Hailing from Redondo Beach, California, Sean’s passion for design and all things mechanical started at birth. Having grown up at race tracks, hot rod shops and car shows, he brings old-school motoring style and a lifestyle bent to his mostly vintage watch collection. He is also the Feature Editor and Videographer for Speed Revolutions.