In the world of mechanical watches, precision reigns supreme. And while Switzerland’s COSC sets the modern standards for chronometer certification, observatory certification was once regarded as the most prestigious certificate for accuracy in mechanical timepieces. Amongst the most famous was the Kew Observatory, known for its extensive chronometer testing regime. Its “observatory trial” tested watches for 44 days under numerous extreme positions and conditions as compared to COSC’s relatively shorter test of 15 days. Sold at the Bonhams Watch Auction were not one, but two extremely rare Kew A tested Rolexes that may be the most highly accurate watches to have gone under the hammer for its time.

Two Kew A Tested Rolex Watches Sold At The Bonhams Watch Auction

Rolex Oyster Speedking

Image: Bonhams Watch Auction

Lot 21 is a stainless steel manual wind Rolex bracelet watch. The Kew A tested movement was granted additional distinction of “especially good” rating. Out of the 136 watches that managed to attain the coveted Kew A certificate, only 16 watches were granted the especially good classification, making this one of the rarest watch Rolex has ever produced. According to Hodinkee report, the Oyster Speedking had a pre-sale estimated value of $7,600 to $10,000. The watch was sold as of 12 December 2018 at SGD$30,347.

Rolex Oyster Observatory Chronometer

The next watch under Lot 22 was an exceedingly rare 18k gold manual wind wristwatch made by Rolex circa 1951. The Rolex Oyster Observatory chronometer with a pre-sale estimated value of $32,000 to $44,000, was one of 24 watches cased up in an 18k gold casing. According to Bonhams, the movement 4156 achieved the Kew A certificate on its 4th attempt through Teddington, placing it under the last batch of watches to pass before they stopped issuing certificates. The watch was sold at SGD$54,191 as of 12 December 2018 at London, New Bond Street.