Standards and methods
Each
officially certified COSC chronometer is identified by a
serial number engraved on its movement and a certification number given by the COSC.
Testing criteria are based on
ISO 3159[9] which defines a wrist chronometer with spring-balance oscillator. Only movements which meet the precision criteria established under ISO 3159 are granted an official chronometer certificate. Compare ISO 3158.
[10]
Each uncased movement is individually tested for fifteen days, in five positions, at three different temperatures. The movements are fitted with a seconds hand and the automatic winding mechanisms are disengaged for the tests. Measurements are made daily with the aid of cameras. Based on these measurements, seven eliminatory criteria are calculated, each of which must be met (e.g., for movements of a diameter over 20 mm, the requirements, indicated in seconds/day, are noted in the table below). There is no ISO standard for quartz timepieces, but there is development in this field. ISO 10553:2003 specifies the procedure for evaluating the accuracy of quartz watches, individually and by lot, and the relationship between the accuracy tested and the accuracy classification given by the manufacturer. It applies to quartz watches having accompanying documents on which the accuracy classification is indicated. Nevertheless, COSC has also developed its own standard for testing quartz chronometers with eight eliminatory criteria, also noted in the table below.
COSC Standards Mechanical Quartz Average daily rate: -4/+6
[11] Average daily rate at 23 °C: ± 0.07 Mean variation in rates: 2
[12] Rate at 8 °C: ± 0.2 Greatest variation in rates: 5
[13] Rate at 38 °C: ± 0.2 Difference between rates in H & V positions: -6/+8
[14] Rate stability: 0.05 Largest variation in rates: 10
[15] Dynamic rate: ± 0.05 Thermal variation: ± 0.6
[16] Temporary effect of mechanical shocks: ± 0.05 Rate resumption: ± 5
[17] Rate resumption: ± 0.05 n/a Residual effect of mechanical shocks: ± 0.05; 200 shocks equivalent to 100 G (981 m/s², 3,217 ft/s²)
Measurements are compared with a time base established by two independent
atomic clocks synchronized on GPS time. Not all chronometers are supplied with the report issued by the COSC as the reports are optional to the brand or maker. Each manufacturer may decide whether to reveal the results gathered during the certification process of the movement. For example, Breitling do supply all their watches with COSC Certificates (all Breitling watches since 2000 are Certified chronometers) however Rolex and Omega do not supply even their chronometer certified watches (not all their watches are certified chronometers) with the COSC certificates. Omega however can provide the COSC chronometer certificate if asked.
The value of COSC certification
[edit] Only 3% of Swiss Watch production is COSC certified
Over a million official chronometer certificates are delivered each year, representing only 3% of the Swiss watch production, a proportion that underscores the exceptional nature of a chronometer. To earn chronometer certification, a movement must not only be made from the highest quality components, but also be the object of special care on part of the finest watchmakers and timers during assembly.
[20]
[edit] Meaningful test or marketing gimmick?
There is a debate among watch enthusiasts as to whether the COSC chronometer certification for a Swiss watch is a meaningful test or a simple marketing gimmick. On the one hand, when a watch maker intends to submit a movement for COSC testing, they frequently employ additional jewelling (i.e. to the barrel) and better quality
[21] "
Ébauche" parts (i.e. higher quality hairsprings, mainsprings, balance wheels; regulators, etc.) all aimed at the coveted chronometer certification.
[22] On the other hand, it is likely that most good quality movements on the market today are capable of being tweaked, and timed to fall comfortably within the benchmark -4/+6 average daily rate criteria of the COSC. However, movements so submitted to COSC are more likely to be submitted with better quality parts in order to be confident of a successful test, and as a consequence may be more likely to maintain better timekeeping rates over the service life of the time piece.
[23]
Therefore, some of the ?Haute Horlogerie? Swiss Watch Manufacturers have created on 5 June 2001,
?The Fleurier Quality Foundation? to establish new aesthetic and technical criteria dedicated to the certification of finished watches. Their certification meets a normative requirement for the market and the final customer to have a better definition of quality watchmaking, adapted to today's demands and technological advances. Geneva's have created along similar criteria the
Geneva seal
[edit] Exemplar brands submitting to COSC
Rolex submit by far the largest number of movements to COSC followed by
Omega SA,
Breitling,
TAG Heuer and
Panerai. .
[24] Breitling submit all movements for certification but other manufacturers only submit certain models.
