What Is a Superlative Chronometer?

What Is a Superlative Chronometer?

There are different spots all along the watch collecting journey, and different questions that arise at each of those milestones. Maybe you’re at the very start of your travels, and you’re still learning the definition of terms such as escapement, rotor, and deployant. Maybe you own a few watches, but you’re still learning about the history or technology behind automatics.

Or maybe you have a pretty robust official collection (as well as an unofficial collection of ill-advised purchases and Frankenwatches in a random dresser drawer.) If that’s the case, you’re fairly knowledgeable when it comes to movements and references. Still, no matter what type of collector you are, it never hurts to go back to basics.

Reviewing the fundamentals of watch construction gives you the opportunity to reflect on the truly incredible history, design, and engineering that undergirds well-made watches. Today we’ll dive into the specific requirements that watches must meet in order to be designated a Superlative Chronometer. Whether you’re new to watches or an experienced horology buff, this article will help remind you what an amazing timepiece you have on your wrist. In fact, some might even call it superlative. 

rolex hang tags

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What Is a Chronometer?  

An officially certified chronometer is the name that the Official Swiss Chronometer Testing Institute (COSC) gives a timepiece that meets incredibly high standards of efficacy and accuracy. Over the course of a 15 day period, COSC performs rigorous testing of a watch’s movement and mechanism. In order to be certified as a chronometer, a movement must lose no more than four seconds per day or gain no more than six seconds per day. This is determined by calculating the average daily rate, the rate variation, and the timekeeping in both horizontal and vertical positions, as well as the accuracy at a variety of different temperature points. 

What is a Superlative Chronometer? 

Obviously, the rigorous standards of accuracy required for COSC-certification disqualify many Swiss watches. It’s very difficult to keep a movement accurate to -4/+6 seconds. If you have a watch that is COSC-certified, it’s a paragon of performance. However, Rolex has always sought to exceed the standards set by COSC. In 1951, it began identifying its watches as Officially Certified Superlative Chronometers, indicating that it met and exceeded current COSC standards. These four words make for a busier dial, but they serve to indicate the commitment to accuracy that Rolex has pursued for years. 

This image is a Rolex Calibre 3135

What is the accuracy of current Rolex movements? 

Around 2015, Rolex began preparing to debut an updated movement, the Caliber 3255. Rolex has its own on-site testing lab, and some would argue that the testing done in-house at Rolex is even more stringent than COSC tests. Rolex’s new movement  kept time with +2/-2 accuracy, more accurate than the highest certification achievable by COSC. Slowly, Rolex began bringing all the watches in its collections, including the hand-wound Cellini, up to the -2/+2 standard, which is quite an achievement. Today, Rolex’s most recent movement, the 3230, is also accurate to this -2/+2 standard. 

A Superlative Watch Strap for Your Rolex 

If you’re looking for a watch strap worthy of one of the world’s most accurate movements, Everest Band’s carefully designed rubber straps fit individual Rolex cases for an unparalleled fit. 


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Written By: Meghan Clark


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