Institutions – Certification bodies & labs

OFFICIAL SWISS CHRONOMETER TESTING INSTITUTE (COSC)

The Official Swiss Chronometer Testing Institute (COSC) is the leading certification authority for Swiss chronometers, ensuring the highest standards of precision in timekeeping.

    History and Evolution

    COSC was founded in 1973 as a collective effort by the Swiss watchmaking industry to establish a standardized and impartial system for certifying the precision of mechanical and quartz movements. It consolidated various regional observatories that previously performed chronometric testing, such as the renowned observatories in Geneva, Neuchâtel, and Besançon.

    The organization was formed to:

    1. Unify Standards: Create a single benchmark for chronometric certification across Switzerland.
    2. Protect Swiss Watchmaking Prestige: Enhance consumer confidence in the accuracy and reliability of Swiss-made timepieces.
    3. Encourage Innovation: Provide a rigorous framework that challenges watchmakers to continually improve their craft.

      Purpose of COSC Certification

      The COSC certification is specifically designed to assess the accuracy of chronometers. The term “chronometer” is legally protected in Switzerland and can only be used for timepieces that have passed COSC’s stringent evaluation.

      COSC certification serves three key purposes:

      1. Guaranteeing Accuracy: It ensures the movement can maintain time within tight tolerances, reflecting excellence in engineering.
      2. Enhancing Consumer Trust: Certification provides a quality assurance mark for customers investing in high-precision timepieces.
      3. Setting Industry Standards: It establishes a universal benchmark, encouraging technical advancements in horology.

          Requirements and Testing Process

          COSC certification involves subjecting watch movements to an exhaustive series of tests for 14 to 20 days, conducted in controlled laboratory conditions. The requirements are among the most stringent in the watchmaking industry, particularly for mechanical movements.

          1. Accuracy Tolerances

          A certified mechanical movement must maintain a daily deviation within -4 to +6 seconds per day, measured over a 15-day period.

          For quartz movements, the acceptable maximum average daily rate deviation is ±0.07 seconds per day at a temperature of 23°C. Additionally, the movement is tested at temperatures of 8°C and 38°C, where the permissible deviation is ±0.2 seconds per day.

          2. Testing Conditions

          • Temperature Variation: Movements are tested at multiple temperatures, typically 8°C, 23°C, and 38°C, to ensure they remain accurate in different environments.
          • Positional Testing: Movements are tested in five positions (dial up, dial down, crown left, crown up, and crown down) to account for performance differences due to gravitational effects.

          3. Performance Metrics

            • Average Daily Rate (ADR): Overall timekeeping precision over the test period.
            • Isochronism: Consistency of timekeeping as the movement’s mainspring unwinds.
            • Rate Variation: Difference in accuracy across tested positions and temperatures.

          4. Certification

          Movements that meet COSC standards receive an official chronometer certificate and are engraved with an individual identification number.

          It is important to note that the certification applies exclusively to the movement before it is put in the case and covered with the dial. However, there exist additional tests of the finished timepiece, with FQF being the best example.

          Key Numbers

          Before the establishment of COSC as an independent entity in 1973, various official state labs were providing accuracy tests and certifications in Switzerland.

          According to the official statistics, in 1976 COSC provided 200,000 certificates, in 2000 – 1 million, gradually increasing this number to 2-2.3 million per year in recent years.