Since its creation in 1973, the Official Swiss Chronometer Testing Institute (COSC) has been tasked with controlling the precision of watch movements and awarding the official title of “chronometer” to successful candidates. This honor is among the most prestigious Swiss labels and certifications: thus, each year, nearly 1.8 million pieces are subjected to the demanding scrutiny of COSC laboratories.

The Establishment of COSC

At the origin of COSC were several Control Bureaus created in different Swiss watchmaking cantons from the end of the 19th century, independent of each other and fiercely competitive. To ensure uniformity of observation and control conditions, as well as consistent pricing, initiatives were launched in the early 1970s (notably through State Councillor René Meylan of Neuchâtel) in favor of establishing an organization to structure the operations of these bureaus.

Thus, the year 1973 saw the creation of the Official Swiss Chronometer Testing Institute, COSC, under the aegis of the watchmaking cantons of Bern, Geneva, Neuchâtel, Solothurn, and Vaud – and the Federation of the Swiss Watch Industry. Established in La Chaux-de-Fonds, a municipality with a rich watchmaking history, COSC retained only three laboratories from those that had been fiercely competing: those in Biel, Le Locle, and Saint-Imier. The objective articulated by Pierre-André Bugnon, the first president of COSC (to end the cacophony that reigned among the various Control Bureaus), was quickly achieved.

COSC, an Organization Guaranteeing Swiss Watchmaking Tradition

The objective of COSC is as follows: to measure the precision of any movement submitted by manufacturers in order to obtain the prestigious “chronometer” certificate. The laboratories conducting the tests are under the responsibility of COSC’s management and must strictly apply the instructions issued by it.

A guarantee of quality and the culmination of exceptional watchmaking craftsmanship, the official “chronometer” title ensures the absolute precision of time-measuring instruments. In this sense, COSC contributes to perpetuating a long-standing watchmaking tradition in Switzerland.

Today, COSC oversees the testing of approximately 1.8 million movements and watches per year (this number was only 200,000 in 1976). Any manufacturer can submit their timepiece to the measurement criteria of the association’s laboratories – whether mechanical or quartz movements. However, in total, only about 6% of watches exported from Switzerland receive “chronometer” certification.

But that’s not all: in addition to establishing precision control criteria, coordinating laboratories, and ensuring the proper functioning of measurement and recording equipment, COSC also undertakes communication initiatives around the concept of “chronometer”.

Demanding and Rigorous Control Criteria

To obtain “chronometer” certification, a watch movement must meet seven precision criteria. These criteria are established by the ISO 3159 standard, which itself forms part of the definition of a “wristwatch chronometer” (a precision timepiece for measuring long durations). Each movement is controlled by criteria adapted to its specificities – thus, quartz watches and mechanical pocket watches meet different requirements.

The pieces submitted for testing by COSC laboratories are examined for a period ranging from 14 to 20 days, depending on the nature of the instruments tested. The series of tests that movements must undergo is static and applied to unmounted instruments (on unfinished watches). Only the best products succeed: those made of quality components and benefiting from the finest craftsmanship throughout the assembly phase. To learn more, visit the official COSC website.

At the end of the process, COSC issues an “official chronometer certificate”. Furthermore, each chronometer is assigned a number engraved directly on the movement, making it unique. The result is a high-value-added certification that distinguishes a movement from the bulk of global production.