COSC Calibership Challenge: Precision on Display at Geneva Watch Days 2025

Key Highlights

• A four-day live regulation contest at Geneva Watch Days 2025 using 40 Sellita movements and 40 contenders.
• Contest pieces subjected to COSC chronometric testing in five positions and three temperatures with optical measurement.
• CEOs, journalists, influencers, collectors, and watchmakers competed under guidance from the Geneva School of Watchmaking.
• 32 out of 40 participants ultimately achieved COSC’s –4 / +6 seconds per day tolerance.
• More than 17,000 visitors discovered COSC certification through an arcade-style video game experience.

At Geneva Watch Days 2025, COSC transformed chronometry into a public challenge. Inside the Pavilion’s Culture Club, the Calibership Challenge invited professionals and enthusiasts to sit at the bench and see how close they could push a mechanical movement toward precision in just one hour.

Working on 40 Sellita movements, 40 contenders raced against the clock under the eye of students from the Geneva School of Watchmaking. They quickly discovered that effective regulation depends on methodical work, a steady hand, and understanding how even small interventions shift the rate.

The mood shifted from discovery to competition as CEOs, editors-in-chief, influencers, collectors, and watchmakers compared results. Journalist Yannick Nardin of WorldTempus placed first, followed by influencer Amandine Perret-du-Crêt and Sowind Group Co-Founder and CEO Patrick Pruniaux. Figures from Bulgari, Laurent Ferrier, Depancel and others completed a top 10 that reflected how widely the culture of precision is shared across the industry.

After each one-hour session, COSC sent the adjusted movements to its laboratories for the same protocol applied to any movement seeking “Certified Chronometer” status. Over several days, the pieces were tested in five positions and three temperatures, with optical cameras tracking the average daily rate according to the ISO 3159 standard.

The comparison between readings taken at the Pavilion and the laboratory results underlined why COSC’s methodology matters. The contest compressed regulation into a single hour, while true chronometer status rests on a 12 to 20-day evaluation against seven ISO 3159 criteria. Even so, 32 of the 40 competitors remained within COSC’s –4 / +6 seconds per day tolerance, showing what targeted adjustment can achieve when guided by a clear standard.

The Calibership Challenge also attracted unexpected profiles. French writer Sylvain Tesson, known for his travel narratives, placed 14th and was among the competitors whose movements met COSC criteria. For COSC, this mix of personalities and the resulting visibility on social media opened the usually discreet world of laboratory testing, operators, and procedures to a much broader audience.

Beyond the Bench: A New Face of Swiss Chronometry

Running alongside the contest, an arcade-inspired video game at the Culture Club introduced more than 17,000 visitors to the principles behind COSC chronometer certification. The playful format showed that rigor, impartiality, and technical mastery can be communicated in simple, intuitive terms.

For COSC’s President, Sébastien Cretegny, the initiative reflects a wider strategy: use major watchmaking events to reach end clients who look for intrinsic quality rather than narrative alone. Geneva Watch Days President Jean-Christophe Babin, the first to attempt the challenge, highlighted how the format demonstrated the patience demanded by watchmaking and the contribution of students from the Geneva School of Watchmaking to the future of the craft.

Why it matters

The Calibership Challenge repositioned COSC certification as a live, shareable experience and clarified the gap between a quick timing snapshot and the depth of full chronometric testing. By involving industry leaders, creators, and the public, COSC reinforced its role as an independent reference for Swiss precision while keeping the conversation around future evolutions of ISO 3159 firmly grounded in measurable performance.

For discerning collectors in the GCC, where reliability in demanding climates is crucial, such initiatives confirm that “chronometer certified” is more than marketing language. It signals movements that have endured a defined, repeatable process, offering reassurance when you evaluate Swiss watches through authorised retailers or specialist advisors.