Many dials say “Chronometer”, “Superlative Chronometer” or “Master Chronometer”. They sound similar but mean different tests. Here we collect what the manufacturers themselves say about them and, above all, which of it can be seen on QC photos at all. Terms like rate deviation and movement are explained in the watch movements and parts glossary.
[[PHOTO: Drei Zifferblatt-Ausschnitte nebeneinander mit den Schriftzügen „Chronometer“, „Superlative Chronometer“ und „Master Chronometer“, darunter jeweils ein Fragezeichen]]
Editorial summary, not independently verified.
The basis is the COSC test, as Rolex describes it: only the movement is tested, before it is cased. It runs for 15 days in five positions and at three temperatures. To pass, it has to show an average daily rate of −4 to +6 seconds.
The key word is “movement”: the COSC test says nothing about how the finished watch runs with its case and dial.
Beginner question: the dial says “Superlative Chronometer Officially Certified”. Does that mean this watch’s movement was tested?
No, text on a dial is just print. On no watch does it prove that this exact movement passed a test.
What Rolex means by Superlative Chronometer: after the COSC certification of the movement, Rolex tests the cased watch again in its own labs. The tolerance is then −2/+2 seconds a day, and power reserve, water resistance and self-winding are tested as well. The green seal goes with it. According to Rolex, further criteria were added in 2026, including on resistance to magnetic fields.
Which Rolex reference has which calibre is in Rolex calibres 3230, 3235, 3285, 3255 and 4131.
Omega takes a different route with the Master Chronometer. According to Omega, the movement is first certified as a chronometer by COSC. After that, the finished watch goes through eight tests by the Swiss Federal Institute of Metrology (METAS), including resistance to magnetic fields of 15,000 gauss. The permitted rate deviation is positive only: 0 to +5 seconds a day, a little more for smaller movements.
[[PHOTO: Schema mit drei Stufen nebeneinander: „Werk allein (COSC)“, „eingeschalte Uhr (Rolex)“, „eingeschalte Uhr, acht METAS-Tests (Omega)“]]
Got it. But then what can you actually check on QC photos or on arrival?
Little that has to do with the certificate. A timegrapher photo in QC is a snapshot in one position, not a 15-day test. What the values mean is in timegrapher in QC photos. On arrival you can check winding, hacking seconds, quickset and power reserve yourself, see arrival check for a rep watch.
The only thing you can check on photos is how the text is executed: even letters, neatly centred, no bleeding ink. That’s a question of print quality, not of timekeeping.
Summary:
- COSC: test of the movement alone, 15 days, five positions, three temperatures, −4 to +6 seconds a day.
- Rolex Superlative Chronometer: an additional test of the cased watch at −2/+2 seconds a day, plus power reserve, water resistance and self-winding; extended with further criteria in 2026.
- Omega Master Chronometer: COSC certification of the movement, then eight METAS tests on the finished watch, including 15,000 gauss.
- Text on the dial proves none of these tests.
- Checkable in QC: only the print quality of the text; a timegrapher shows a snapshot.
Not checkable on photos: water resistance, timekeeping over several days and the movement itself.
Editorial summary, not independently verified.
Thanks. Point 4 was exactly my question.