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Rolex Kew A Certified Speedking Oyster ‘Observatory Chronometer’

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Rolex Kew A Certified Speedking Observatory Chronometer

Rolex ‘Kew A’ speedking, one of the rarest Rolex watches in the world. Around 1950 Rolex announced that they had send around 100 of their small men’s watches for chronometer testing to the Kew A Observatory chronometer institute in the UK. The watches submitted for testing where tested for 44 days in five positions and at three temperatures.

140 Rolex watches where awarded with the kew A certificate, the watch we offer for sale is one of those very few historical important Rolex watches. Rolex was very proud on the achievement and shared this in their marketing statements as shown in the pictures below.


rolex kew a advertisement

The Kew A Observatory chronometer institute

The term chronometer means that a watch remains a certain accuracy per day. The most known certification for chronometer standards today is the Swiss Cosc. Other observatory chronometer institutions are the Besancon Observatory in France and the Kew Observatory in England. The British Kew Observatory had the strongest tests and therefor chosen by Rolex for their testing program with the 140 Kew A Rolex watches. The Kew Observatory still exist today and we got the original testing records from this particular ‘Kew A’ Rolex watch.


Rolex Kew A Speedking ref 5056

The Rolex Speedking dates back to the 1940’s and was designed as a small mens watch with a diameter 23.7mm. The condition of the watch is great and it remains in original condition. The dial remains untouched as well as the blued steel hands, the movement bears the Kew A certification with number 4183, from the records we received from the Kew Observatory we can conclude that this specific movement was certificated with first testing (some examples had been tested multiple times to achieve the Kew A certification).

Fun fact, the Rolex Kew A mentioned in official Rolex Advertising had to be send back twice for a final certification. This might explain why some examples have the Guillaume balance wheel while others (like the one we have) bear the monometallic (Glucydur) balance. From our research we know 8 pieces with the Guillaume balance wheel, 5 pieces with the monometallic balance and another 8 unknown.

All Rolex Kew a watches and movements are constructed my Rolex master watchmaker Jean Matile. Matile selected the very best parts from various Rolex calibers from, the 700 series for the assembling of the movements send to the observatory chronometer institute. Also custom made parts not seen in other models are used for those selected movements.

Condition and guarantee

This Rolex Speedking remains fully original, only part changed during the years is the original clasp. The old style jubilee bracelet is still intact, however the clasp has been changed for a generic clasp with no brand. The service history is unknown but seeing the historical value we didn’t thought a service would be necessary, of course we can deliver the watch with a full service on request. The watch comes with 1 year guarantee anyway and we guarantee the watch to be fully original. A true historical important and rare Rolex watch for the serious watch collector, here some links to articles about the Kew A Rolex chronometer.



Vintage Times

Vintage Times Amsterdam is a small watch boutique who mainly deals online and with a select group of private collectors. We are constantly looking for rare vintage timepieces and try to present the best condition available. Please don’t hesitate to get in contact for more information about this watch or other timepieces from our collection. We ship worldwide and also welcome you for a visit at our office in Amsterdam

Vintage Times

email: [email protected]

tel / app: +31 6 4 1111 044