By Harlan Chapman-Green

The world of watches is impressive. It’s vast, full of ideas which are well presented (mostly). Horology, unlike a lot of different industries, is something that intertwines history with the future. Some watches are cheap, affordable and low maintenance; something which can be used for daily wear by those uninterested in timepieces. Other watches take hand craftsmanship to different worlds, even so far as developing new techniques and tools to achieve something never seen before. But, for all of this, who is responsible for setting the standards? What are the requirements for a watch? How do we examine a watch? This article will look at the different standards agencies set up which offer professional accreditations for watches. They have some different requirements, but most of them are either focused on timekeeping performance or the finishing and detailing of a watch.

COSC (Contrôle Officiel Suisse des Chronomètres)

COSC is by far and away the most well known of the regulating bodies in the watch industry, and it tests over 1.6 million watches a year. COSC will examine any watch, and lots of companies put different types of watches with all manner of complications in them through the test, although Rolex and Omega test more watches than any other companies. They only award the certificate to watches which meet a set criteria of accuracy and are tested under laboratory conditions with the movement outside of the case (COSC can also test watch heads, but commonly they only examine calibres). When a movement arrives at the COSC labs, it is verified to ensure it has been sent by the manufacturer. It’s then wound to the level specified by the manufacturer and kept for at least 12 hours in a room which is exactly 23 degrees Celsius so that the materials have time to stabilise. The total time for testing is 15 days for mechanical watches, 13 for quartz watches and 19 days for carriage clocks.

COSC has different requirements for different watch types, as it can test both mechanical watches and quartz timepieces. For a mechanical watch with a balance spring, there are seven criteria which must be met:

Average daily rate: This is the difference between the time the watch displays and the time of the two atomic clocks that COSC uses over the first ten days of testing. The requirement is -4 to +6 seconds per day.

Mean variation of rate*: The mean rates of five average daily rates, taken within the first ten days of testing. The limit is 2 seconds per day.

Greatest variation of rates*: The absolute value (i.e. not rounded) of the largest of the rate variations. The limit is 5 seconds per day.

Difference between rates in horizontal and vertical positions: This is self-explanatory, but it is calculated by subtracting the average daily rates for 9th and 10th days of testing from the rates for the 1st and 2nd. The limit is -6 to +8 seconds per day.

Most significant variation in rates: The largest difference between the average daily rates and one of the rates from the ten days of testing. The limit is 10 seconds per day.

Thermal variation: This is calculated by measuring the rates at 8 degrees Celsius and 38 degrees Celsius, the results of the former are subtracted from the latter and then divided by the temperature difference (30). The limit is +/- 0.6 seconds per day.

Rate resumption: The difference between the test on the last day and the average results from the first two rates. The limit is +/- 5 seconds per day.

Note: Requirements marked with an asterisk (*) make specific use of the results from 5 different positions as individual numbers, rather than a grouped result of all the results combined into an average. Because the movements are tested in various positions (3 O’clock, 6 O’clock, 9 O’clock, dial facing up and dial facing down), the balance speed may be affected which in turn affects accuracy.

As you can see, the requirements are quite specific, but they are all necessary to ensure a watch runs as accurately as possible. The results do not get rounded, that means if something is even 0.05 seconds over or under the requirement the watch does not get certified. Unfortunately, the COSC tests have faced a few problems, mainly over the fact that they are not representative of the watches in a real-world environment (and they do not do physical shock testing), which they do state on their website. Also, because manufacturing has become extremely advanced, it is possible to make a mainstream watch movement run within the specifications set out by COSC.

Poinçon de Genève

The Poinçon de Genève, otherwise known more commonly as the Geneva Seal or the Seal of Geneva, is a very highly regarded standard in the watchmaking industry. Unlike the COSC regulations above which cater to accuracy and performance, the Geneva Seal instead looks more at the quality of construction and decoration of a movement, although there are performance elements. Further, it also guarantees authenticity because it is a location specific accreditation, parts (the escapement, escapement setting, the setting itself, the repassage and the adjustment) of the watch must be made by employees of a company who live in the Canton of Geneva. As well as this, assembly, casing, adjustments and testing must be carried out in the City of Geneva.

The requirements set out by the Geneva seal are quite technical which means I may use a little jargon here and there. Most decoration requirements are set so they remove the marks left over from the cutting and machining processes. We have tried to make it as understandable as possible as we know it can become difficult to follow, even for those who love their watches. For the most part, you could think of it as “if it is there, it has to be decorated”. However, it’s not that simple.

Baseplates, bridges and plates for complications must have polished chamfers on their edges. The sides of these must be straight grained as well, and any marks left over from machining must be removed by circular graining or other finishes. Any recesses or bevelling holes, and any sink-holes for jewels must also be polished. Further, the supports for bridges should be smoothed down and the tops of said bridges should either have a Geneva stripe finish, or any other decoration which removes the marks from machining. Any jewels on the bridge side must be semi-brilliant with a polished sink, but there is no requirement for a centre-wheel endstone on the baseplate.

The going train (the gears which divide the power into logical parts, i.e. hours, minutes and seconds) has its requirements. The wheels and their hubs must have a chamfer on them on both sides unless the wheel is 0.15mm or less, in which case only one chamfer is needed due to structural rigidity purposes. The wheels must have sinks (the stepped section around the centre of the wheel), the shape and position are up to the manufacturer, but they must be polished. Again, if the wheel’s thickness is less than or equal to 0.15mm, only one sink is required. All functional parts relating to the pivots must be burnished, while other parts must be finished to remove marks from machining. Manufacturers are left to finish the pinions and their teeth, but the finish must not round off edges, flatten burs or modify the functional parts of the teeth. Any jewels on the train must be semi-brilliant with a polished sink.

Any wheels and pinions not in the going train must be finished to remove the signs of machining, and they must be polished if the material used is suitable for it. Any wheels which aren’t solid (i.e. they have crossing beams) must be finished in the same style as the wheels on the going train. If possible, the teeth of the ratchet-wheels and the crown-wheels must be chamfered and polished if they are thick enough to allow for it. All machining marks must be removed via decoration.

For any other parts and plates of the movement, any high-quality jewel or bearing is allowed.

In general, shaped parts must have smoothed facets, polished chamfers, straight grained sides to remove the marks of machining and a levelled or finished topside. However, more complex pieces require other procedures. Domed screw heads must be circular grained or polished and sit in a chamfered slot, the same goes for flat headed screws which also need a chamfered edge. Any pins must be polished, regardless of whether they are flat or domed. As long as the finish works, colouring is also allowed, along with machine and chemical trimming/polishing procedures, as long as they respect the regulations for decorations. Any pieces which have been folded are okay, as long as they are finished so that the folding is undetectable. For springs there are yet more requirements. Edges of strip springs and jumper springs must be chamfered, unless the spring is 0.18mm thick which could affect the stiffness of the spring, in which case this is not needed.

When a company applies for a Geneva Seal, it must send an assembled movement, along with 2D designs of the movement, a set of all individual components from the movement and any additional components. Once approved, the applicant company must then send another assembled movement and a reference list of all parts. Once the watch is authorised the seal, the manufacturer will then be observed at every stage while making the watch, but special inspections are always carried out before, during and after movement assembly.

Finally, the watches and their complications are tested in their cases. The manufacturer must tell the Geneva Seal office how it is checking the watches, and these procedures are then verified when the manufacture is audited. If the watch is water resistant, it must be at least 30 meters resistant; then they will test to that level instead. The accuracy requirements are not as stringent as COSC. Watches must not deviate by more than one minute over the course of the 7 day test they undertake, if there is a chronograph it must be running for at least 24 hours. Also, the power reserve must be equal to or exceed what the manufacturer states.

There’s a lot to cover for this one, but you know the watches are of excellent quality if they have received this certificate.

METAS (Federal Institute of Metrology)

METAS is the Swiss Government’s body for measurements, measurement methods and measurement procedures, although it is the new kid on the block when it comes to watches. It is the only body currently able to award the rating of ‘Master Chronometer’, that means that the watch has been tested to a higher level of chronometric performance than those which come from COSC. While the watch laboratory is currently based inside the headquarters of Omega in Biel for practicality reasons, METAS will test any watch sent its way.

METAS certification is technically an additional certificate, as any watch going for it must have passed the COSC testing first and received a chronometer rating.

Average daily chronometric precision: Over four days the watches the watches are put int 6 different positions, two temperature zones and will be subjected to high magnetism, after this their readings are taken and compared to before the tests began.

The function of COSC-approved movement under a magnetic field: This is a hard test to pass for most timepieces. The watches are subjected to 15,000 gauss for 30 seconds in two positions; a microphone is used to test their accuracy.

The function of a watch under a magnetic field: This is precisely the same as above, except now the movement is inside its case which is more representative of actual wear.

Deviation of daily chronometric precision after magnetic exposure: Calculated using results before and after magnetisation, this test shows whether the magnetic field has had any long-term effects on the watch, showing the minimal deviation between the two days.

Power reserve duration: This test is designed to ensure the watches run to at least the limit stated by the manufacturer.

Deviation of chronometric precision over the course of power reserve: The point of this test is to ensure that the accuracy of the watch is constant between 100% of power in the barrels and 33%., this is where the most significant drop in precision would typically occur.

Deviation of chronometric precision in 6 positions: One-upping the five of COSC, the watch is checked in six different positions, the deviations between the upper and lower extremes of this test are displayed.

Water resistance: All watches are tested to their water resistance limit to ensure they can perform under everyday punishment. Any diving watches tested must endure pressures which exceed their stated maximum to ensure their performance and durability is high.

METAS certification could be a thing of the future, the main drawbacks currently are that it takes more time to test the watches in total, and that it’s officially recognised but very limited in its capabilities right now. METAS doesn’t yet have a laboratory as COSC does, so it can’t expand testing right now.

This article turned out to be a lot longer than I had initially anticipated, so I have split it into two parts to make it more readable for everyone.

The Jargon Buster will return.