Reference
Master Chronometer: What METAS Tests, and the 694 Watches Here That Passed
Since 2015 Omega has had its cased watches certified against eight tests, including a 15,000 gauss magnetic field. Seventeen calibers and 694 watches in this library carry the certificate. What it measures, and what it does not.
"Master Chronometer" appears on the dial of most current Omegas, and it is easy to read as a slogan. It is a certificate, issued by a Swiss federal body, for a test programme that no other standard in the industry runs. In this library 694 watches across seventeen calibers carry it, out of 2,921 mechanical Omegas.
Two certificates, in order
The first is the familiar one. The COSC, the Swiss chronometer testing institute, tests a bare movement over fifteen days in five positions and at three temperatures, and passes it if the daily rate stays between −4 and +6 seconds. Every Master Chronometer movement is a COSC chronometer first.
The second is METAS, the Swiss Federal Institute of Metrology, which since 2015 has certified the cased watch — the movement, dial, hands and case as sold — against eight criteria. The watch must run correctly while exposed to a magnetic field of 15,000 gauss, and its rate after exposure must still be within 0 to +5 seconds a day. Its precision is measured over four days in six positions and at two temperatures, so the tolerance is tighter than the COSC's and applies to the assembled watch. The power reserve must match the claim, the rate must hold between full wind and a third of the reserve, and the water resistance must match the dial. METAS audits Omega's test line rather than running its own, and every watch is tested, not a sample.
Why 15,000 gauss is the headline
A conventional hairspring is a steel alloy, and a magnet can leave it sticking to itself, which makes the watch run fast by minutes a day. The old defence was a soft-iron cage around the movement, which stops the display back and adds thickness. Omega's answer was materials: a silicon balance spring, which cannot be magnetised, and non-ferrous alloys through the escapement. The 2013 Aqua Terra >15,000 Gauss proved the approach, and METAS was set up to certify it. The figure is the strength of a magnetic resonance scanner; a fridge magnet is a few hundred gauss, and the watch is indifferent to both.
The calibers, and where they sit here
| Caliber | Family | Reserve | Watches here |
|---|---|---|---|
| 8800 | Single barrel, mid-size cases | 55 h | 243 |
| 8900 | Two barrels, 41 mm and up | 60 h | 89 |
| 8700 | 27 mm and 29 mm cases | 50 h | 62 |
| 9900 | Chronograph | 60 h | 44 |
| 8806 | 8800 without date | 55 h | 39 |
| 8701 | 8700 with Sedna gold rotor | 50 h | 38 |
| 8807 | 8800 with Sedna gold rotor | 55 h | 35 |
| 3861 | Hand-wound Moonwatch chronograph | 50 h | 35 |
| 8912 | 8900 without date, Ultra Deep | 60 h | 28 |
| 8801, 8901, 8906, 8704, 8705, 9901, 9904, 9906 | Gold-rotor, GMT and moon-phase variants | 81 |
The pattern is that Master Chronometer is a specification, not a movement. Omega applied it to the 8500 architecture to make the 8900, built the smaller 8800 and 8700 to it from the start, extended it to the 9300 chronograph as the 9900, and in 2019 rebuilt the fifty-year-old Moonwatch movement to it as the 3861. The Globemaster of 2015 was the first watch certified; the Aqua Terra, with 174 Master Chronometer references here, is where most of them live, followed by the Constellation, the Seamaster Diver 300M and the De Ville.
What came before
The 694 sit beside a larger group that is co-axial but not Master Chronometer: 398 watches on the ETA-based 2500, 167 on the 8500 and 193 on the 8520. Those movements share the escapement and, from 2011, the silicon spring, but were certified by the COSC alone. Some late 8500-family watches carry "Master Co-Axial" on the dial, the anti-magnetic construction before the METAS programme existed; it is not the same certificate.
How it compares
Rolex's Superlative Chronometer, set in 2015, also tests the cased watch and to a tighter rate, two seconds a day either way, but it does not test magnetism to a published figure and it is Rolex's own programme rather than a federal one. Patek Philippe's Seal is a broader standard covering finishing and service as well as rate. METAS is narrower and more measurable: it certifies that a specific watch, as sold, kept a specific rate under a specific magnetic field.
Each caliber above has its own page listing the watches here that carry it, and the glossary covers the power reserve the test measures and the caliber it is applied to.