Letter From the British Horological Institute to Rolex on the Subject of the Record Kew Certificate

Before 1914, the Kew Observatory in Great Britain had never granted a "Class A" certification to a wristwatch. These certifications were generally given to large marine chronometers that went through rigorous testing until Rolex submitted a wristwatch to prove that they could be just as precise. On July 15, 1914 they proved the skeptics wrong by submitting a small watch that looked like the one photographed below and making it the first wristwatch to ever receive Kew Certification. With this accomplishment, Rolex began manufacturing more certified chronometers than any other watchmaker in the industry at the time.

A Rolex Watch Comparable to the First Class A Chronometer (photo: Rolex)

The testing took place over 45 days and included testing the precision of the tiny wristwatch in five different positions. It was also submitted to extreme temperatures, ice-cold and burning-hot, and also ambient temperature. The stringent testing was necessary because the precision of the marine chronometers of the time was necessary to ensure the safety of the ships that depended on their accuracy. The Rolex watch submitted for testing was precise up to +1 second.

Kew Chronometer Results (photo: Rolex)

Rolex continued to manufacture certified chronometers while it developed other advances in watchmaking. By 1926, they introduced the Oyster case, a waterproof case that is still in use today on most Rolex models. In 1931 they introduced the self-winding Perpetual rotor that is also still used today to power most automatic mechanical watches. After 1951, when it became compulsory for all watches to pass certification, the watchmaker made sure all of its movements received particularly good results through 1971, when those citations were no longer issued. Since then, Rolex has come up with its own Superlative Chronometer Certification.

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