Audemars Piguet Royal Oak Double Balance Wheel Openworked – 15407ST.OO.1220ST.01

If there's one thing Audemars Piguet knows how to do, it's openworking. The brand's manufacture dedicates an entire room to skeletonising luxury watch movements (I wrote about the manufacture, and the Audemars Piguet brand , in detail in a watch producer profile)—and so specialised are the people in this room that many perform expert roles within the overall process. There's a guy who only fits balance wheels into the ultra-thin Calibre 5122, and others who spend hours delicately removing all but the structural metal from the in-house movements.
The basic function of skeletonising a luxury watch is to show off the quality of the movement. It's thought that André-Charles Caron, a Parisian watchmaker, was the first to do this. In the late 1700s, Caron decided to lay open the faces and plates of his watches so the public could glimpse the inner mysteries of the fine horological machines he created. It was a stroke of marketing genius. To a true watch geek (and there were plenty of watch geeks around in the 18th century), nothing can beat the sight of the infinitesimal parts of a well-made movement, ticking and pulsing and whirring like the organs of a mechanical bird.
The Audemars Piguet Royal Oak Double Balance Wheel Openworked ( Audemars Piguet reference no: 15407ST.OO.1220ST.01 ) makes the utmost of its naked movement, revealing the PR-worthy heart of the calibre: the double balance wheel, which AP claims improves accuracy by 30% (the figure is calculated by looking at comparable movements that lack the double balance wheel).
The balance wheel and escapement are the seat of all accuracy in mechanical watches, and the centuries-old goal of fine watchmakers has been to increase this accuracy by mitigating the effects of gravity, orientation, and temperature (among other considerations) on them. Unfortunately, the delicate and entirely non-digital parts of a mechanical watch are extremely susceptible to fluctuations in just about any environmental factor you care to name. That's why lovers of luxury watches are so concerned with the specifications of watch calibres. The Contrôle Officiel Suisse des Chronomètres (COSC) certifies movements as 'COSC Officially Certified Chronometers' if they demonstrate an accuracy of -4/+6 seconds per day. Some brands, like Rolex, create their own in-house accuracy ratings to highlight the fact that their luxury watches perform with even greater accuracy than the COSC standard.
I can't find exact figures for the +/- seconds accuracy of the Audemars Piguet Royal Oak Double Balance Wheel Openworked: but it's safe to say that fans of the brand (who are legion) and fans of highly technical luxury watch movements (ditto) will both be attracted by the double balance wheel, which sits in an off-centre balance cock, under a stunningly, traditionally finished, gold bridge. Beneath it, the twin balance wheels beat at 3 Hz (21,600 vph), flickering frantically from side to side in their quest to defray the effects of gravity and wrist movement.
Here's how those balance wheels work: they're connected by a pin, but they operate independently. The theory is that the aggregate accuracy of the pair will turn out to be greater than the individual accuracy of each one: so when one wheel is experiencing fluctuations in accuracy due to the orientation of the wearer's wrist (for example), the other one, operating at greater accuracy, will pick up the slack—and vice-versa. Note that accuracy and good running aren't the same thing: the movement's power reserve of 45 hours, and its self-winding capability, ensure the watch remains well-wound, but as with any mechanical watch the Double Balance Wheel Openworked will need to be regulated periodically to ensure it keeps good time.
The rest of the movement is skeletonised with the care, skill, and attention to finishing that we've come to expect from Audemars Piguet. The power reserve isn't registered (indeed, the movement displays simply central hours, minutes, and seconds with its lumed pink gold hands, and applied pink gold hour markers). But it doesn't need to be. Aside from the fact that the mainspring can be seen through a skeletonised barrel, who wants to be distracted with dials and indicators, when they could be marvelling at the almost biological operation of a perfectly-designed movement?
The Audemars Piguet Royal Oak Double Balance Wheel Openworked features a case diameter is 41 mm, and the case itself is in stainless steel. Front and rear crystals are sapphire glass. The bracelet is also stainless steel, secured by a hidden folding clasp that pins a steel AP buckle in place.
The Royal Oak is a classic. Openworked watches are inherently beautiful, and AP openworked watches are the stuff of horological legend. The Audemars Piguet Royal Oak Double Balance Wheel Openworked, then, is the real deal. It takes all the things a watch-lover really enjoys about luxury watches—the superb mechanical design, the finishing, the painstaking solutions to the problem of regulation—and makes them beautiful. A spectacular luxury watch.
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