Quality Assured

Justin Ng lays out the industry standards for certified precision watches

- Justin Ng

What good is a watch that does not keep precise time – even if it has a fancy tourbillon, a beautiful enamelled dial and a strap in the supplest of calfskin? At the centre of watchmaking, no matter the brand or style, is the steadfast pursuit of precision, and only a watch with exceptional accuracy can earn chronometer certification. Many watchmakers take pride in setting the bar even higher, subjecting their watches to a battery of comprehensive internal and external tests before conferring them with noble certifications.

COSC CERTIFICATION

Responsible for certifying the accuracy of Swiss watches, independent testing institute Contrôle Officiel Suisse des Chronomètres (COSC) assesses movements according to the Iso 3159 standard. For 15 days, the watches undergo daily testing where they are kept in various positions, inside thermal enclosures corresponding to the different temperatures required. Each piece remains in a given position and temperature for 24 hours, and every day, it is briefly removed from these thermal enclosures to be measured, using machine vision systems with five cameras.

The seven criteria upon which a movement is judged: the average daily rate, the mean variation in rates, the greatest variation in rates, the difference between rates in horizontal and vertical positions, the largest variation in rates, the variation in rate depending on temperature, and the rate resumption. Only upon meeting set numbers for each one of them is a movement certified as chronometer.

It is also commonly publicised that COSC-certified chronometers stay within the -4/+6 seconds per day variation, but this is the minimum requirement; many often keep better time and brands have no hesitation in boasting of chronometric movements inside their watches, proudly displaying the word “chronometer” on the dial.

FLEURIER QUALITY FOUNDATION