In 1914, the Kew Observatory in Great Britain granted a “Class A”
certificate to a wristwatch for the very first time. This major
achievement by a small Rolex watch astonished the world and
marked the advent of the modern precision wristwatch.


Until then, such a certification, which attested to the highest
chronometric precision, had generally been awarded only to large
marine chronometers after extremely rigorous tests. Rolex was the
first to prove that a wristwatch could be just as precise as a marine
chronometer – something that was scarcely believable at the
time. This performance would contribute significantly to the rise
of the wristwatch. On the strength of this success, Rolex would
become the world’s largest manufacturer of chronometer-certified

wristwatches. The brand perfected the concept of the modern
watch in 1926 by inventing a waterproof Oyster case to protect
the movement and then, in 1931, by developing the self-winding
Perpetual rotor movement. Today, all Rolex Oyster models are
officially certified chronometers, the heritage of the pioneering
role played by the brand in bringing precision to the wristwatch.

A feat of miniaturized precision

By obtaining the very first “Class A” rating certificate for a wristwatch
from the Kew Observatory near London, on 15 July 1914,
Rolex accomplished an exploit that would forever change the
destiny of the modern watch. A feat of miniaturized precision, this
first chronometer wristwatch met with flying colours the British
observatory’s demanding criteria, the most stringent in the world:
45 days of tests, in five different positions and at three different
temperatures (ice-cold, oven-hot and ambient). For the first time
in history, a wristwatch fulfilled the requirements expected of the
best marine chronometers. These navigation instruments, whose
precision was used to determine the position of ships at sea
(longitude), could not deviate by more than a few seconds per day
without putting the safety of the ships at risk. The Rolex wristwatchchronometer
certified by Kew 100 years ago recorded an average
daily rate of only +1 second.

The wristwatch gains legitimacy at Kew


The man behind this feat was Hans Wilsdorf, who founded Rolex
in 1905. By obtaining this first chronometer certificate from Kew,
he demonstrated that, in terms of precision, a small wristwatch
made by Rolex could rival the best of timepieces – including pocket
watches, which were the norm at the time. In those early days of
the 20th century, no one had yet managed to design a truly reliable
and precise wristwatch. Wristwatches were not favoured at the
time, as the small mechanism could not compete with the regularity
and reliability of the larger pocket watch movements. However,
since the beginning of his career, Hans Wilsdorf had been firmly
convinced that the wristwatch would be future of the watchmaking
industry. He devoted the energy of his youth to eliminating all the
weak points of the wristwatch.The quest for precision was his first
1914, A MILESTONE IN WATCHMAKING HISTORYobjective. This visionary entrepreneur was firmly convinced that
precision was essential to secure the acceptance and popularity of
the wristwatch.


From a utopian dream to the chronometer wristwatch


Nearly two centuries after John Harrison designed the first marine
chronometer, Rolex targeted equal precision for a wristwatch. The
first success came in 1910 when the brand succeeded in obtaining
a chronometer certificate for a small watch from the Official Watch
Rating Centre in Bienne, Switzerland. In 1914, Rolex designed and
produced a chronometer wristwatch whose precision equalled
the most sophisticated measuring instruments of the era and had
it certified by the Kew Observatory. Its performance was unheard
of; endorsed by the most prestigious official observatory in the
world, it would contribute decisively to the rise of the wristwatch.
Until then, making the wristwatch into a reliable, robust, highprecision
device had been the stuff of utopian dreams. But Hans
Wilsdorf demonstrated that precision in a small format was not only
conceivable but also achievable. This distinction by Kew was an
official recognition of the highest world-class quality for Rolex and
held the promise of a bright future for the wristwatch. From then on,
to maintain its leading position in the manufacture of high-quality
precision wristwatches, Rolex made it a point of honour to develop
mechanical movements that were certified as chronometers by
observatories and official watch rating centres.

The rise of the wristwatch

While officially certified by chronometer certificates, the precision
attained by the Rolex wristwatch remained much more vulnerable to
shocks, dust and humidity than that of pocket watches. Therefore,
Rolex’s next objective was to design a perfectly waterproof case
to protect the movement and maintain its certified precision. This
was accomplished in 1926 with the invention of the Oyster, the
world’s first waterproof wristwatch, thanks to an ingenious patented
case system featuring a screw-down bezel, case back and winding
crown. The name, Oyster, was inspired by its capacity to remain
indefinitely submerged in water without risk of damage. It was
not only waterproof, but also dustproof, for dust is a formidable

1914, A MILESTONE IN WATCHMAKING HISTORYenemy of watch movements. To further perfect its watches, Rolex
developed in 1931 the Perpetual self-winding system, which
winds the mainspring via the action of a free rotor driven by
wrist movements. There was no longer a need to wind the watch
manually with the winding crown, a critical point for maintaining
waterproofness. This self-winding system, also patented, ensured a
constant power reserve and regularity of rate.
The Rolex Oyster Perpetual thus accumulated three fundamental
qualities: it was precise, waterproof and self-winding. These
advantages would provide an extraordinary stimulus for the Swiss
watchmaking industry and the contemporary mechanical watch.


Rolex, historic leader in timekeeping

A true pioneer in chronometer wristwatches, Rolex made certified
precision its signature. By the early 1950s, Rolex had manufactured
nearly 90 per cent of all chronometers officially certified in
Switzerland since 1927 — the year specific criteria for wristwatches
were introduced. When, in 1951, the regulations changed and it
became compulsory to obtain chronometer certification from an
official body, Rolex went further and made sure its movements
obtained certificates bearing the citation “particularly good results”.
This distinction gave rise to the famous phrase still inscribed on
Rolex dials today: “Superlative Chronometer Officially Certified”.
Since the creation of the COSC (Swiss Official Chronometer Testing
Institute) in 1973, special citations are no longer given on the
certificates. But the signature on Rolex dials remains as a reminder
that since the early 20th century, Rolex has played a central role
in the development of the modern precision watch. The brand’s
leadership in chronometric precision continues to the present day,
as Rolex is the largest manufacturer of chronometer-certified watch
movements in the world.