A type of certificate that confirms the quality of a watch before leaving the factory, the COSC standard certificate is very familiar to the Swiss watch industry and is often reserved for watch models produced in large quantities.

So what is the COSC standard? What is the importance and use of this type of certificate? Any questions surrounding the term “COSC standard” will be revealed by Watch World in the article below! Let’s follow along!

I. What is a Chronometer watch?

Chronometer watches are a term used to refer to highly accurate watches, capable of displaying seconds and have been rigorously tested through many rigorous tests over many days, in different positions and at different temperatures. In other words, Chronometer watches are Swiss watches that have achieved Chronometer quality certification issued by COSC.

II. What is COSC certification on watches?

COSC (Contrôle Officiel Suisse des Chronomètres) is an official Swiss inspection organization founded in 1973. The main task of this organization is to test and certify the accuracy of wristwatches. Movements of many world famous brands such as Rolex, Omega, Tissot,…

COSC certification is given to watches that have been tested and meet COSC’s precision standards. This body will be responsible for ensuring that the watch movement will run accurately and reliably under all operating conditions. The watch movement will be tested based on ISO 3159 standards within 16 days of testing in 5 positions, 3 different temperature levels and they must maintain the required accuracy (only deviations of about – 4 to +6 seconds per day).

COSC tests the accuracy of watches by measuring the accuracy of the watch’s internal movement over a long period of time. Standard movements will be shipped back to the company to be assembled into the watch and completed before leaving the factory. They will be inspected again by the company to ensure 100% completion.

Normally, for every 100 machines sent for inspection, up to 95 machines are certified. Because COSC only tests the movement, when installed in the watch, there will be some deviations in parameters but not significant. In addition, the data inspected by the organization will be kept on the system for 5 years.

III. Standards for COSC certification

To be certified to COSC standards, both the watch and the movement must be manufactured and assembled in Switzerland, have the Swiss Made label and will have a serial number engraved on the movement to mark the certification.

The movement sent to COSC will be subjected to an inspection process: The watch movement will be fitted with a 5-groove clasp, the movement will be wound according to the instructions, the components will be placed in a heat-controlled casing degrees at 23 degrees Celsius within 12 hours.

After that, the apparatus will be tested continuously for 15 days at different temperature levels. A watch meets COSC standards when it meets the following conditions:

The average error after the first 10 days ranges from -4 to +6 seconds/day.

The speed of the clock movement runs fast or slow at 5 different points (2 horizontally and 3 vertically each day). To qualify, within 10 days, the device must reach 50 points and the error must not exceed 2 seconds.

The highest change time in 5 different positions is no more than 5 seconds/day.

COSC subtracts the vertical mean value from the horizontal mean value and the deviation should be between -6 and +8 seconds.

The difference between the maximum error of the day and the average error of the day does not exceed 10 seconds/day.

The apparatus when tested at 8 degrees Celsius and 38 degrees Celsius with an error not greater than 0.6 seconds/day.

The difference between the average speed during the day on the first and last two days of testing should not exceed 5 seconds.

IV. Target watch brands want COSC certification

Most Swiss watch brands today want COSC certification and are not afraid to race to achieve this standard, the reason is because:

COSC certification helps increase the value of watches because of the reputation for quality it brings. Because the likelihood of meeting the COSC standard is very low, watches with this certification will certainly have a higher value than those without this certification.

Limited quantity by year: On average, only more than 1 million COSC certificates are officially provided each year, accounting for 3% of the total output of Swiss watches produced, so there are only high quality watches. only, carefully assembled and made from the best materials can achieve this certification.

Because the COSC test is so rigorous and demanding, achieving this standard is considered solid evidence that the watch’s performance is very reliable.

Certification of watches made by leading experts with high technical qualifications and skills.

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