Wednesday, September 5, 2007

Inside COSC

COSC stands for Contrôle Officiel Suisse des Chronometres (official Swiss chronometer inspection). Furthermore, in 2001, COSCs three laboratories in Geneva, Biel and Le Locle, individually tested 1,315,752 horological movements, almost all for compliance with international chronometer standard ISO 3156 for mechanical wristwatches, and issued 1,255,515 chronometer certifications worth at least USD4.5 million. This is a 23.3% rise on the previous year.

Out of 77 brands and a handful of watch schools submitting movements for chronometer certification, Rolex is by far the biggest contributor to COSC. It sends almost their entire output of mechanical movements to COSC and in 2001, 761,601 of them were given chronometer certificates — a 20% increase over 2000. "All the mechanical watches Rolex sells are officially certified chronometers," intoned a bimbo in charge of misinformation at the Geneva company headquarters. The Geneva and Biel laboratories are almost entirely devoted to testing Rolex movements. Interestingly, Geneva, where 96% of movements tested are from Rolex, shows the lowest failure rate at 2.2%. It rises to 4.5% in Biel (86% Rolex) and to 5.7% in Le Locle where virtually no Rolex movements are tested.

Top Six COSC Brands in 2001


Rolex - 761,601 - All mechanical + 573 quartz mvmts, men's and women's
Omega - 207,879 - All mechanical, men's
Breitling - 142,825 - 40% quartz
Bulgari - 36,380 - All mechanical, men's
Panerai - 27,275 - All mechanical, men's
Tag Heuer - 20,650 - All mechanical, men's

Audemars Piguet, Jaeger-LeCoultre, Lange, IWC, Breguet and Piaget are among the brands absent from COSC.

What Does COSC Measure and How Good is the Test?

In order to satisfy the insatiable apathy of his readers for the most irrelevant details, Watchbore went in person to the COSC laboratory in Geneva to see for himself how the movements are tested. "We test the engine and not the car; that is the responsibility of the brand," says Mr Curchod ushering Watchbore into the dust-free, temperature- and moisture-controlled climate of the laboratory. COSC tests movements at their barest functional level, although brands can enter movements with as many complications as they like. As all the movements are wound by the crown, automatics have to leave their rotors behind because the machine that turns the crown would damage the highly geared winding mechanism. Most of the mechanical watches tested by COSC become automatics. Each movement is fitted with a COSC standard dial, seconds-hand (sweep or small) and winding crown. Every 24 hours, an electronic camera records the state of the seconds-hand to the nearest tenth of a millisecond compared to the atomic reference clock. The camera shoots twice in succession to check whether the movement has stopped. Then the movement is rewound and returned to the appropriate position and temperature for the next 24-hour period. This goes on for 16 consecutive periods. For the first 11 periods, the movements spend at least 48 hours in each of five positions at a constant 23°C. The readings indicate both how accurate and how precise the movement is. Using a shooting analogy, accuracy is how close you are to the target. Precision is a tight grouping of shots, which may be off target. Thus, a watch that gains 15 seconds a day might not be accurate, but if it gains (or loses) exactly the same amount every day, it is extremely precise. High precision can be adjusted to accuracy, but low precision indicates inherent faults such as an inconsistent power supply, probably due to defects in the going train. By analyzing the rate variation between different positions, the COSC test can diagnose a badly poised balance, too much oil, or a need to review the profile and roundness of the pivots. The next three test periods determine how much the rate varies between three different temperatures — 8°, 23° and 38°C. Excessive changes in the rate could show that the balance-spring alloy is not up to standard. For the last two days, the movement resumes its original position and temperature. Comparing the readings here with the first two days’ results shows to what extent the test itself has affected the performance of the movement. Rolex has a special machine to test its vast quantities of movements. These are loaded into magazines like bullets. The machine extracts the movement, reads it, winds it and returns it to the magazine. Non-Rolex movements are placed in recesses on trays. In an adjoining room, large cupboards hold batches of watches in various positions at different temperatures.


Mean daily rate (during the first 10 days): -4+6 secs/day

Mean rate variation (average of the 5 absolute variations in 5 positions during the first 10 days of test): 2 secs/day

Maximum rate variation (in five positions during the first 10 days of test): 5 secs/day

Maximum difference in rate between vertical and horizontal positions (mean rate of days 1 and 2 minus mean rate of days 9 and 10): -6+8 secs/day

Greatest rate difference (between one of the first 10 daily rates and the average daily rate for the test): 10 secs/day

Rate variation according to temperature (the rate at 38°c minus the rate at 8°c divided by the temperature difference): ±0.6 secs/day °c

Rate resumption (the final rate minus the average rate of the first two days): ±5 secs/day

Why COSC Doesn’t Grade Watches According to Performance

The objective assessment and testing of civilian watches started in the railway age when confidence in the timekeeping qualities of your watch became paramount. Observatories and laboratories in major cities rated timepieces. Manufacturers competed for prizes. Customers paid premiums for high-rated watches. COSC differs in one important respect from all previous watch testing institutions and observatories. It is strictly non-competitive. There are no points awarded or any prizes. There are no degrees of success or honorable mentions. The watches either pass or fail. This was the one condition demanded by the Swiss watch industry when COSC was founded in 1973. Until that time, there were two institutions in Switzerland that issued rating certificates to watches. The observatories rated prepared timepieces, held competitions and awarded prizes. Local testing laboratories in seven watch making towns issued rating certificates to time-of-day watches. These were grouped into an association called ABDO. ABDO rating certificates gave commendations such as "especially good" to deserving movements. Ninety percent of the watches submitted to ABDO laboratories were from three brands — Rolex, Omega and Mido.In 1972, an important delegation of Swiss watch manufacturers went to see Mr René Meylan, then industry minister in the Neuchâtel cantonal government. They demanded the end of the observatory competitions. The reason: the Japanese had swept the board in the last two events. Mr Meylan replied that he thought that the whole point of the competitions was for the best to win. The brands then threatened to boycott the contests. Meylan gave in. The observatory competitions were suspended and never revived. At the same time Rolex, Omega and Mido started to dismember ABDO. By selectively boycotting one or other of the seven testing laboratories they caused each to grant increasing discounts and favors until the organization collapsed. Mr Soguel says COSC does not compile or publish comparative results because there is no demand for it from the brands. He compares the COSC certificate to a university degree. "It certifies that you have reached a certain standard, but it does not guarantee that you can still pass the test 20 years hence. And when you frame your diploma on your office wall, you don’t mention the marks you got." Were COSC to introduce any sort of ranking by test results, Swiss watchmakers would be forced to compete on the intrinsic qualities of their watches and the whole value hierarchy of Swiss watches would be overturned.

Is COSC Really Independent?

COSC rose from the ashes of ABDO in 1973 as an association of the five watch making cantons of Bern, Geneva, Neuchâtel, Solothurn and Vaud. This government membership was intended to give COSC official independence, but the association is controlled by its general assembly of government and industry representatives. Although the governments have a majority of one, the quorum rules enable a majority of the brands if any government delegates fail to attend.Mr Soguel declares that the main aim of COSC is to defend its chronometer certificate as a label of excellence, and that maintaining COSC’s total independence from the watch industry is key to the defense of the chronometer. His strategy is uncompromising integrity in the tests. Since he took over as managing director in 1997, COSC has invested heavily in developing its measuring systems and in complying with standards governing testing procedures and environment. The Swiss Federal Office of Metrology has also accredited the COSC laboratories. "I am aware that COSC is a monopoly and of the danger that implies," says Mr Soguel. "But I cannot endanger the credibility of COSC with any lapse from absolute rigor."An increasing number of manufacturers are submitting their movements for chronometer certificates, mostly minor brands with a handful of pieces. Rolex, which accounted for 80% to 90% of the COSC chronometers, has now seen its share drop to 64%. "Rolex has shown a very strong desire that COSC remains totally independent," observes Mr Soguel.After much consideration, Watchbore must reach the conclusion that COSC is either an independent institution or a marketing tool for Swiss brands, but it cannot be both. Even though COSC is a monopoly, it is unable to raise chronometer standards and thus the standards of Swiss watch making. Even though it is a government association, COSC cannot or will not publish the results of its tests. Three brands provide 90% of its turnover. COSC has to be dependent on their goodwill.

besed on article by Alan Downing, at
(full article at

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