In 2016, Audemars Piguet debuted a world-first landmark accomplishment for chronometry, inside of the Royal Oak line: this ref. 15407ST, the Double Balance Openworked. The double balance here does not work on resonance or through a differential like some others. Instead, both balances share a pivot but are mounted vertically stacked, 180 degrees out of phase with each other. This counters positional errors while adding doubling the effective balance wheel mass. The result is one highly precise and accurate Royal Oak. The resulting calibre 3132 was Openworked and debuted in the 41mm Royal Oak case.
Prior to the 15407ST, most attempts at dual synced oscillation in wristwatches used dual hairsprings with a single balance wheel. Where things like the Duality and Resonance have independent balances which are then synced through various means, the 15407ST balanced are coupled structurally. The doubled effective mass here only creates greater inertia and hence consistency, much like marine chronometers of antiquity with massive oscillators.
Despite the true technical innovation here, the greater impression is made by Audemar Piguet's Openworking. The accomplished of the calibre 3132 has so far always been reserved for Openworked models to put AP's full abilities on display. Where much of Audemars Piguet is no longer hand finished, the entire Openworked 3132 is, and masterfully. Interior angles have not been shied away from and there are many. Anglage is entirely performed by hand and the design of the skeletonisation has been engineered with this in mind. Parts of the gear train and keyless works have been given micro beveling on their teeth as well. The base bridges are treated in gunmetal to create a subdued dial impression which blends with steel. It is capable of 45 hours of reserve and still just 4.4mm thin.
The dial itself is constructed largely of these treated grey bridges, though sparing use of gold is used to guide the eye. The balance bridge, for example, is executed in pink gold to highlight its accomplishments. The luminous handset is also in pink gold, pointing at pink gold indices mounted to a thin anthracite chapter ring. The AP signature spans where the 12 marker would normally sit, keeping the view of the watchmaking unobstructed.
The Double Balance Openworked represented a refocusing on chronometry and true handwork within the modern Royal Oak, where many other modern references have opted for more streamlined manufacturing processes. From a watchmaking perspective, it is one of the more significant models to debut in the Royal Oak platform since the 5554, ahead of the RD2 or 26735. As a result, it has become the defining Royal Oak of the last decade, setting aside complications. Though its heart is complicated the rest of the watch has a beautiful harmony and purity of purpose. This is a celebration of modern and traditional watchmaking techniques uniting towards a far more refined Royal Oak.
