Inside COSC

Watchbore investigates the only organization in the world that decides
whether a watch is a chronometer or not.

There are three questions that dominate the forums at TimeZone: How good is my
watch? Is it really worth all the money I paid for it? and, Am I mad?

Watchbore also gets a lot of email asking the same three questions, and his
invariable answers are: It’s as good as you think it is; No, and Probably.

For all its flaws, there is one organization that provides some sort of standard
by which to judge a watch. In his constant search for choice trivia with which
to thrill his readers into a definitive stupor, Watchbore succeeded in
infiltrating the secretive COSC organization, and with the help of his Albanian
associates, secured some valuable confessions from the high priests of this
obscure cult.

But first, some exciting facts based on documents that were recently handed to
Watchbore anonymously by an unknown woman in the street.

They reveal that COSC stands for contrôle officiel suisse des chronometres
(official Swiss chronometer inspection). Furthermore, in 2001, COSC’s 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.

Mechanical Movements (ISO 3156)

1,254,248 1,198,043 56,175 4.5%


Quartz Movements (COSC Standard)

61,504 57,442 4,062 6.6%


The Rolex Factor

These documents, secured at great expense by Watchbore, also rip apart the veil
of secrecy surrounding the exact annual production of Rolex mechanical watches.

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.

Watchbore estimates that at least 15,000 Rolex movements failed in 2001.
According to Rolex, the rejects are fixed and sent back to COSC until they pass.
“We don’t use COSC to tell us how good our movements are,” said a source
deep inside the Wilsdorf foundation. “We test them ourselves. All we want is
the chronometer certification. It’s for marketing.”

Top Six COSC Brands in 2001

Rolex 761,601 64% All mechanical + 573 quartz mvmts, men’s and women’s
Omega 207,879 17.4% All mechanical, men’s
Breitling 142,825 11.4% * 40% quartz
Bulgari 36,380 3% All mechanical, men’s. 70% increase over 2000
Panerai 27,275 2.3% All mechanical, men’s
Tag Heuer 20,650 1.7% All mechanical, men’s

* % of total quartz & mechanical.

The World’s Most Accurate and Precise Movement Revealed

It becomes clear that virtually all mechanical movements gaining COSC
chronometer certificates are what the industry calls “tracteurs” —
the 28,800 v/h workhorses such as the Rolex 3035, ETA’s 2892 and Valjoux 7750.

But the essential question hanging on the lips of the few readers still
struggling to keep awake is: “What is the best-performing caliber of them all?”
Watchbore asked the person most likely to know, Mr Jean-Pierre Curchod, former
dean of the Geneva Watchmaking School, president of the Swiss Society of
Chronometry and director of the Geneva laboratory of COSC.

For an official institution to reveal this information would throw the entire
watch industry in disarray. To hold up one movement as superior to all the
others would deflate the bubble of myth that sustains the tightly linked cartel
of brands. Therefore, according to COSC, all chronometers are equal, and if any
are more equal than others, it’s a state secret.

However, Watchbore soon discovered that he and Mr Curchod happened to share an
interest in the wines produced by a certain Mr Hutin in Dardagny, and it was in
the course of a thorough examination of the relative merits of the Merlot and
the Pinot Noir that a source close to Mr Curchod made a startling revelation.

Now, among all the assorted WISes, watch enthusiasts and experts that frequent
TimeZone to tell the world what watches they wear, it is extremely unlikely that
any owns a watch with the world’s best performing movement. It is equally
unlikely that the woman who owns a Rolex automatic Oyster Datejust is aware that
the caliber 2235 automatic inside is the most consistently precise and accurate
movement tested by COSC.

Even more amazingly, at less than 20mm, the Rolex 2235 falls into the smallest
category where the tolerances are at their widest, yet performs well within the
tightest allowances reserved for pocket-watches. Almost 200,000 of these
movements passed the COSC test in 2001. Does Rolex have a secret? “It’s
their immense know-how in construction and manufacturing,” says Mr Curchod

What makes the chronometer? Watchbore put the question to COSC’s managing
director, Mr Pierre-Yves Soguel. For the best chance of passing the test, the
movement has to be conceived and engineered from the outset as a chronometer, he
explains. It’s all in the design, construction and especially in the machining
of the parts. The most precise machine tools are only viable in high-volume
production, which explains why the mass-produced tracteurs are
consistently chronometers.

According to Mr Curchod, good lubrication is also an essential attribute of the
COSC chronometer. Free-sprung or indexed balances, Breguet or flat springs,
coaxial or lever escapements or tourbillons make little or no difference to
performance in the COSC test. “It’s the quality of workmanship throughout
the movement rather than any single feature that makes a movement accurate and

What about those expensive, lovingly handcrafted crafted, pursuit-of-perfection
in-house movements? It is possible for such movements to reach chronometer
standard, acknowledges Mr Curchod, but at the cost of much expensive and
time-consuming tweaking. “It is more difficult and the failure rates are high
— as much as 60%.”

Other Significant Brands Submitting to COSC

Baume & Mercier 10,416 All Men’ss
Chopard 7,776 Incl. 7272 L.U.C calibers, all men’s
Zenith 5,556 All men’s, incl. 85 pocket & 23 clocks
Vacheron Constantin 3,038 All men’s
Ebel 2,837 All men’s
Ulysse Nardin 2,253 All men’s
Patek Philippe 1,286 All men’s
Chronoswiss 198 All men’s
Girard-Perregaux 2 Both 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

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.

The COSC testing program is divided into 16, 24-hour periods. The watch is
rated in five positions and at three temperatures.

Period (day) Temperature Position
0 23°C 6 o’clock up/ 12 o’clock up (pocket-watches)
1 23°C 6 o’clock up/ 12 o’clock up
2 23°C 6 o’clock up/ 12 o’clock up
3 23°C 3 o’clock up
4 23°C 3 o’clock up
5 23°C 9 o’clock up
6 23°C 9 o’clock up
7 23°C Dial down
8 23°C Dial down
9 23°C Dial up
10 23°C Dial up. Chronographs run 24 hours
11 8°C Dial up
12 23°C Dial up
13 38°C Dial up
14 23°C 6 o’clock up/ 12 o’clock up
15 23°C 6 o’clock up/ 12 o’clock up


Mean daily rate: during the first 10 days. -4+6 secs/day -5+8 secs/day -2+5 secs/day
Mean rate variation: average of the 5 absolute variations in 5 positions during the first 10 days of test. 2 secs/day 3.4 secs/day 1.5 secs/day
Maximum rate variation: in five positions during the first 10 days of test. 5 secs/day 7 secs/day 2.5 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 -8+10 secs/day ±4 secs/day
Greatest rate difference: between one of the first 10 daily rates and the average daily rate for the test. 10 secs/day 15 secs/day 7 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 ±0.7 secs/day °c ±0.35 secs/day°c
Secondary error: the difference between the average rate at 38°c and at 8°c (days 11 and 13) and the average rate with the dial up at 23° (days 9 and 10). not applicable not applicable ±4.5 secs/day
Rate resumption: the final rate minus the average rate of the first two days ±5 secs/day ±6 secs/day ±2.5 secs/day


Why COSC Can’t Raise the Standards

Just about every working watchmaker has a Witschi machine that listens to the
watch and gives the performance of the movement in real time. It is on these
real-time readings that most mechanical watches are adjusted. But COSC still
rates wristwatches according to the static and temperature tests established for
pocket-watches in the late 19th century. The ISO 3159 chronometer
standard, developed entirely by the Swiss watch industry, is more than a quarter
of a century old; 95% of movements submitted pass the COSC test. Isn’t it time
to raise the standard and update the test?

Alas, says Mr Soguel, COSC’s hands are tied, and to change the status quo
would be extremely dangerous.

The reason is that Britain, France and Germany have dropped out of the ISO
committee on chronograph standards, leaving Switzerland in a minority against
India, Japan and China. If Switzerland tried to change ISO 3159, these three
countries could sabotage the Swiss watch industry by imposing a standard that
mechanical movements would find impossible to meet. That would mean the end of
mechanical chronometers, of COSC and of one of the Swiss watch industry’s main
marketing planks.

Breitling Dominates Quartz

Nevertheless, COSC has managed to modernize the test for quartz chronometers.
The old test gave chronometer certification to watches that came free with the
breakfast flakes, and COSC wanted to give the latest thermo-compensated quartz
movements the same status as mechanical chronometers. The new 20-day
environmental test for the certification of quartz-crystal chronometers subjects
the cased-up watches to a total of 7800 100G shocks from six directions,
continuously changing positions, magnetic fields, extreme temperature and
humidity, and expects them to keep time within 7/100ths of
a second a day.

Quartz Movements at COSC, 2001

Breitling 54,140
Krieger (Miami Beach) 1,956
Rolex 573
Radiant (Barcelona) 526
Ventura 238
Sector 9


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

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.

And Finally, What is a Chronometer?

With the bottom of his bottle of Mr Hutin’s best Gamay in sight, Watchbore
feels that it is time to bring this tiresome stream of drivel to its welcome end
by getting to the point. Namely, what is a chronometer?

Watchbore’s Oxford dictionary says it’s an instrument for measuring time
specifically applied to time-keepers having a special escapement and a
compensation balance, used for determining longitude at sea, and for other exact
observation. His Webster’s concurs with: “an instrument measuring the
passage of time with great accuracy, esp. one used in navigation for determining

However, COSC’s very survival depends on the definition enshrined in the
international standard — a “precision watch, rated in different temperatures
and positions and which has obtained an official rating certificate.” Since COSC is the
world’s only body that provides “official” certificates (as a government
organization), it vehemently defends this definition. Any manufacturer claiming
its watches are chronometers without having a COSC certificate is open to
prosecution for “unfair competition.”

The only watchmaker Watchbore knows who flouts this rule is F. P. Journe.
“They can take me to court if they like, but they don’t own the definition
of a common word.”

As Watchbore put away his notebook and prepared to leave the Geneva COSC
laboratory, Mr Curchod took him to one side. “I want to show you a real
chronometer,” he whispered, taking a metal box from a drawer. The movement
inside had Russian markings and all the attributes of a chronometer —
compensation balance free-sprung on a helical spring, pivoting-detent
escapement, fusée and chain. Russia is the only country that still makes marine
chronometers for finding longitude at sea. (Girard-Perregaux markets them under
the John Harrison name.)

Does COSC issue chronometer certificates to genuine marine chronometers? Yes,
but only in Le Locle where they are rated as “table clocks”.



Copyright © Alan Downing, 2002

© 2012 Bourne In Time Inc.