COSC

ChronometerChronometer Certificatechronometer certificationContrôle Officiel Suisse des ChronomètresCOSC (Official Swiss Chronometer Testing Institute)Precision testing
COSC is Contrôle Officiel Suisse des Chronomètres, the Official Swiss Chronometer Testing Institute, which is the institute responsible for certifying the accuracy and precision of wristwatches in Switzerland.wikipedia
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Seiko

Hattori SeikoHattori Seiko Co.lorus
The Japanese have largely abandoned the accolade, replacing it with in-house testing to a slightly more strict standard as with, for example, the Grand Seiko.
The new caliber also met the Grand Seiko Standard, a chronometer certification that the company claims to be more strict than the Chronometer Certificate in Switzerland.

Observatory chronometer

chronometer
At one time the French provided similar large scale testing at the Observatory at Besançon, however, today only a very few watches are currently tested there and carry the accolade "Observatory Chronometer".
The observatory testing regime typically lasted for 30 to 50 days and contained accuracy standards that were far more stringent and difficult than modern standards such as those set by COSC.

Rolex

TudorOyster DateRolex Australia
The Saint-Imier and Biel laboratories are almost entirely devoted to testing Rolex movements.
In 1910, the first watchmaker to earn chronometer certification for a wristwatch (1910) Rolex is the largest manufacturer of Swiss made certified chronometers. In 2005, more than half the annual production of COSC certified watches were Rolexes. To date, Rolex still holds the record for the most certified chronometer movements in the category of wristwatches.

Chronometer watch

chronometerchronometerscertified
Founded in its current form in 1973, the COSC is a Swiss non-profit organization that tests Swiss Made chronometers.
In Switzerland, only timepieces certified by the Contrôle Officiel Suisse des Chronomètres (COSC) may use the word chronometer on them.

Besançon Astronomical Observatory

BesanconObservatory at Besançon
At one time the French provided similar large scale testing at the Observatory at Besançon, however, today only a very few watches are currently tested there and carry the accolade "Observatory Chronometer".
The tolerances for error were much finer than any other standard, including the ISO 3159 chronometer standard that other testing bodies such as COSC use.

Breitling SA

BreitlingLéon Breitling
Although not all Rolex watches are chronometers, Breitling has claimed that since 2000 all of its production is COSC certified.
As part of 10th anniversary of a Breitling–Bentley Motors partnership, the Bentley B04 GMT, B05 Unitime and B06 (based on COSC Certified Breitling Calibre B04, B05 and B06 respectively) were produced.

ETA SA

ETAETA movementsETA S.A.
Thus, based upon the movements used by Rolex, Breitling, and Omega, the movement calibers that obtain most of the COSC certificates are the Rolex 3135 (since 1988) (and variants 3155, 3175, 3185, 4130) and 2235, the ETA 2892A2 (and variants) and Valjoux 7750, each of which operates at 28,800 beats per hour.
One workhorse of the ETA mechanical line is the ETA 2824-2, The 2824 is an automatic winding, twenty-five jewel movement, available in four executions or grades: Standard, Elaborated (improved), Top and Chronometer.

Geneva Seal

Fleurier Quality FoundationPoinçon de Genève
Geneva's have created along similar criteria the Geneva seal.
Precision testing, however, is an option in the inspection process.

Nonprofit organization

non-profitnon-profit organizationnonprofit
Founded in its current form in 1973, the COSC is a Swiss non-profit organization that tests Swiss Made chronometers.

Swiss made

SwissSwiss watchSwiss watchmaking industry
Founded in its current form in 1973, the COSC is a Swiss non-profit organization that tests Swiss Made chronometers.

Acronym

initialismacronymsinitials
COSC is an acronym for the organization's French name, Contrôle Officiel Suisse des Chronomètres.

French language

FrenchfrancophoneFrench-language
COSC is an acronym for the organization's French name, Contrôle Officiel Suisse des Chronomètres.

International Organization for Standardization

ISOInternational Organization for Standardization (ISO)ISO standard
Notwithstanding, the normative standards are set by international agreement and are the same whether they are nominally labeled ISO or DIN standards.

Glashütte Observatory

On the other hand, the Germans have set up their own testing facility in Saxony at the Glashütte Observatory where the DIN 8319 standards, which mirror the ISO standards used by COSC, are employed.

Canton (country subdivision)

cantoncantonscanton seat
The organization was founded by five watchmaking cantons of Switzerland: Bern, Geneva, Neuchâtel, Solothurn and Vaud, together with the Federation of the Swiss Watch Industry (FHS).

Canton of Bern

BernBernecanton of Berne
The organization was founded by five watchmaking cantons of Switzerland: Bern, Geneva, Neuchâtel, Solothurn and Vaud, together with the Federation of the Swiss Watch Industry (FHS).

Canton of Geneva

GenevaGenevanRepublic of Geneva
The organization was founded by five watchmaking cantons of Switzerland: Bern, Geneva, Neuchâtel, Solothurn and Vaud, together with the Federation of the Swiss Watch Industry (FHS).

Canton of Neuchâtel

NeuchâtelNENeuchatel
The organization was founded by five watchmaking cantons of Switzerland: Bern, Geneva, Neuchâtel, Solothurn and Vaud, together with the Federation of the Swiss Watch Industry (FHS).

Canton of Solothurn

SolothurnSOSolothurn, Switzerland
The organization was founded by five watchmaking cantons of Switzerland: Bern, Geneva, Neuchâtel, Solothurn and Vaud, together with the Federation of the Swiss Watch Industry (FHS).

Canton of Vaud

VaudVDCanton de Vaud
The organization was founded by five watchmaking cantons of Switzerland: Bern, Geneva, Neuchâtel, Solothurn and Vaud, together with the Federation of the Swiss Watch Industry (FHS).

Federation of the Swiss Watch Industry

Swiss watch manufacturersFederation of the Swiss Watch Industry (FHS)Fédération de L'industrie Horlogère Suisse
The organization was founded by five watchmaking cantons of Switzerland: Bern, Geneva, Neuchâtel, Solothurn and Vaud, together with the Federation of the Swiss Watch Industry (FHS).

Biel/Bienne

BielBiel, SwitzerlandBienne
They are in Biel/Bienne, Saint-Imier/BE and Le Locle.

Le Locle

Le Locle NELocle
They are in Biel/Bienne, Saint-Imier/BE and Le Locle.

Omega SA

OmegaOmega WatchesOmega brand
Omega also has much of its production certified.

Valjoux

7750
Thus, based upon the movements used by Rolex, Breitling, and Omega, the movement calibers that obtain most of the COSC certificates are the Rolex 3135 (since 1988) (and variants 3155, 3175, 3185, 4130) and 2235, the ETA 2892A2 (and variants) and Valjoux 7750, each of which operates at 28,800 beats per hour.