The COSC has announced a significant evolution in how Swiss precision will be measured. For more than fifty years, the organization has certified movements according to the ISO 3159 standard, a benchmark that helped define the reputation of Swiss watchmaking. Now, in response to the way mechanical watches are worn and engineered today, COSC is introducing a second, higher tier of certification. This new level is called the COSC Excellence Chronometer, and it adds stricter performance requirements that apply to the complete watch rather than only the uncased movement.
COSC states that it is introducing an additional level of certification that is an extension rather than a replacement of the existing standard. It explains that the life of a mechanical watch has changed over the past half century, with greater exposure to magnetic fields, longer power reserves, and more intensive daily wear. The new standard is meant to reflect that reality.
What Is Changing: A New Measurement Standard
The COSC Excellence Chronometer introduces three measurable requirements that go beyond the traditional chronometer test. These are the material changes.
Tightened precision on the complete watch
After the movement passes the classic fifteen day ISO 3159 test, the fully cased watch undergoes five additional days of evaluation. During this phase, the average daily rate must fall between minus two and plus four seconds per day. This measurement follows a period of semi dynamic wear simulation using a robot that mimics average wrist motion.
Verified magnetic resistance
The complete watch must maintain its performance after exposure to a magnetic field of two hundred Gauss. This requirement acknowledges the increased presence of magnetic fields in daily life and the growing use of anti magnetic materials in modern movements.
Confirmed power reserve
COSC will now verify that the power reserve matches the manufacturer’s stated specification. This is a practical addition, since longer power reserves have become common and are often used as a selling point.
These three elements form the core of the new standard. They represent a shift from testing the movement alone to evaluating the watch as a finished object.
How the Method Works
The process unfolds in two stages. First, the movement is tested for fifteen days according to the seven criteria of ISO 3159. Only after it passes this stage does it return to the manufacture for casing. The complete watch then undergoes five days of additional testing. COSC notes that it tests one hundred percent of watches individually and never relies on sampling.
What This Means for the Industry
The new standard arrives at a moment when the landscape of watch certification has become more competitive. METAS has popularized cased watch testing and magnetic resistance. TimeLab, Chronofiable, and the Fleurier Quality Foundation each offer their own approaches to measuring quality. Brands themselves have also stepped into the space with internal standards that often exceed COSC tolerances.
In this environment, COSC is reinforcing its role as the central authority for Swiss precision. The Excellence Chronometer creates a hierarchy of performance. The traditional Certified Chronometer continues as the established benchmark. The new standard becomes the pinnacle for brands that want to demonstrate a higher level of technical achievement.
