Some Oysterquartz dials have “Superlative Chronometer” on them and some don . Were some Oysterquartz models not chronometers?
The Oysterquartz Datejust models that were made in the first couple of years of production are the ones without the chronometer wording on the dial. These watches use the Mark I 5035 movements, which were not submitted to the COSC for “official” testing. All Mark I and Mark II Day-Date movements were certified chronometers, and these models had “Superlative Chronometer Officially Certified” on the dials from the beginning. The COSC accuracy requirements for a quartz chronometer equate to an annual deviation of no more than 25 seconds. How does that square with Rolex’s unofficial claim of 60 seconds per year and the fact that the later Oysterquartz watches were “officially certified” chronometers? The short answer is that it doesn’t square. The current more stringent COSC requirements for quartz chronometers were put into effect in 2001. That year Rolex received 573 chronometer certificates for Oysterquartz movements, and this was the last year that they received any certificates for qu
