Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm

The Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm, Reference 15467OR.OO.1256OR.01, features the Manufacture Calibre 3132, first seen in January 2016. The ‘Double Balancier’ is a patented mechanism that delivers superior precision and stability. However, beyond its technical benefits, this movement showcases flawless finissage and, courtesy of openworking, a captivating visual appearance.

This detailed review of the Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm, Reference 15467OR.OO.1256OR.01 includes images, specification details and pricing.

Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm

Precision is an overriding obsession

In the esoteric domain of haute horlogerie, precision is an overriding obsession. Over the years, numerous hours have been expended in the pursuit of consistent accuracy.

Abraham Louis Breguet identified that gravity could have an adverse affect on the regulating organ of a watch. His solution was the ‘tourbillon’, or whirlwind. The entire escapement (the balance, hairspring, pallet level and escape wheel) was placed in a rotating cage. This cage would typically rotate 360° in one minute, negating any gravitational errors. Breguet patented his invention in 1801 and it continues to be used to this day.

A problem experienced with some hand-wound watches is the issue of consistent torque from the mainspring supplying the balance. As the energy held within the mainspring depletes, the magnitude of the force serving the balance reduces. This causes the amplitude to fall, reducing oscillations and compromising precision. Various solutions have been conceived to address this problem, including the fusée and chain and the rementoir.

There are other factors which can influence precision

A hairspring with an overcoil, a hand-applied curve bent upwards and attached near the balance staff, is designed to achieve isochronism. This is where the oscillations of the hairspring are constant, irrespective of the amplitude. Effectively, the hairspring ‘breathes’ symmetrically and evenly. An overcoil is usually the preserve of fine watches.

An index-adjuster, or curb-adjuster, alters the rate of a watch by changing the effective length of the hairspring. If the effective length of the spring is shortened, the movement will run faster. The problem with this approach, typically found on cheaper watches, is that the spring is nipped, impairing isochronism. Furthermore, the balance is more susceptible to positional errors.

A superior solution is to equip a movement with an inertia-free balance or variable-inertia balance. The length of the hairspring is fixed and the rate is adjusted using weights or masselottes. This approach counters the disadvantages usually associated with index-adjusters and is a specification detail often found on high-end watches. Sometimes the masselottes are positioned in-board to mitigate air turbulence around the balance wheel, again, augmenting precision.

The double balance wheel

In 2016, Audemars Piguet unveiled the Royal Oak Double Balance Wheel Openworked 41mm, offered in a choice of steel or 18-carat pink gold. This model incorporated a new movement, the Calibre 3132. Although this movement was based on the venerable Calibre 3120, it represented a new chapter in the company’s history and a huge leap forward in the world of haute horlogerie.

The Calibre 3132 is endowed with a double balance wheel with two balance springs, both sharing the same axis. The two balances are the aforementioned variable-inertia type, each fitted with eight, in-board masselottes. By having two balance wheels, one accessible from the dial-side and the other from the rear of the watch, the movement is more balanced, further aiding precision.

Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm

Beyond its technical virtue, the fitment of a double balance wheel confers incredible views of each balance, whether the watch is admired from the front or back. Needless to say, this ‘world-first’ was patented by the esteemed Maison. The benefits of improved precision and stability (the consistent rate keeping of a watch, irrespective of whether it is fast or slow) will resonate with all purists seeking horological excellence.

Earlier this year, Audemars Piguet launched a new model equipped with a double balance wheel, the aptly named Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm. With the advent of this model, the brand from Le Brassus has provided a new audience for its cutting-edge, Calibre 3132. This new timepiece will sate the desires of many ladies seeking a paragon of watchmaking excellence. However, the unisex styling of this model should equally appeal to those gentlemen preferring the neatness of a 37mm case.

Openworking (skeletonisation)

In 1934, Paul Louis Audemars and Paul Edward Piguet decided to revisit the art of skeletonisation after this historical technique had fallen out of favour. From the very beginning Audemars Piguet’s openworked timepieces were made completely by hand, a practice which continues to this day. Indeed, it is the filing, decoration and finishing by hand which confers superior aesthetic and technical characteristics. Openworking has since become another speciality of this prestigious Maison.

Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm

When openworking movement parts, the watchmaker removes superfluous material, heightening the visual allure of the calibre. However, this operation requires great skill to ensure that the torsional rigidity of the movement is not compromised. If the resultant work has reduced the stiffness of the mainplate or bridges, then the reliability of the movement may be impaired. In addition, removing too much material may undermine the shock resistance of the movement. The watchmaker will avoid touching those vital parts necessary for the safe running of the watch e.g. jewel beds and screws.

After all surplus material has been removed, using a fretsaw, or similar, all cut elements and exposed components must be finished using techniques such as chamfering, polishing, brushing, decorating or engraving. Audemars Piguet performs all of these tasks by hand.

The Calibre 3132 fitted to the Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm harnesses all of the esteemed company’s openworking expertise. Each surface is pared back to the essential, imbuing the movement with a high degree of transparency. CNC machines (Computer Numerical Control) could have been used to mill parts, obviating the need to use the aforementioned labour-intensive methods described. However, while this may have proved suitable for external and rounded angles, it would never deliver the highly-prized interior angles, or v-cut angles, coveted by purists. Interior angles require filing by hand. The files are of varying coarseness and used to create a 45° angle.

There are numerous internal angles on the Calibre 3132, testament to the skill of AP’s workforce and the exacting standards of this historical firm.

The dial

A potential problem with openworked watches is that the dial area can appear cluttered, impairing readability. Thankfully, no such issue afflicts the Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm. The pink gold Royal Oak hands articulate the time wonderfully. Both the hour and minute hands feature luminescent coating, enhancing visibility, especially in restricted light. The matching pink gold hour markers are also endowed with luminescent treatment, aiding read-off. A particularly attractive aspect of the dial is the way the hour markers seemingly float in mid-air, augmenting the allure of the dial still further.

Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm

The final function is the central sweep seconds hand. It eschews any luminescent coating, features a counterweight and virtually kisses the minuterie presented on a flange, aiding interpretation.

With the design of this watch, Audemars Piguet has sated many of my horological fetishes. I always enjoy examining a movement at close quarters, absorbing all of its finely finished features. Anglage, with its coquettish capacity to flirt with light, abounds. Circular grained wheels are ubiquitously presented. Perlage adorns the mainplate and can be seen adjacent the crown wheel. Centre stage, the hour and minute wheels are clear to see. The openworked barrel cover, featuring four spokes, reveals the mainspring in various states of wind.

However, beyond this horological titillation, the pièce de résistance is the gorgeous golden balance bridge, occupying the southwesterly portion of the dialscape. Affixed to the mainplate with a gleaming screw at each end, the bridge offers greater stability than a balance cock affixed with one screw. The bridge is openworked and bevelling adorns the rounded, exterior and interior angles. The upper variable-inertia balance, featuring in-board masselottes, stands testament to AP’s  punctilious standards. The balance spring is secured with a sliding stud cap with rounded head as best practice dictates.

A key attribute of the double balance wheel is that each balance wheel can be adjusted from either the dial side or movement side, as appropriate. Moreover, the wearer can observe the balance in flight from either the front or rear of the watch.

The case

When Gérald Genta conceived the original Royal Oak in 1972, arguably the greatest sports watch designed to date, he had the novel idea of integrating the bracelet into the case. Prior to this, all watches featured conventional lugs. The Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm upholds this design element. By seemingly uniting the watch head and bracelet, the design is wonderfully cohesive.

While I like some of AP’s Royal Oak Offshore models, in my opinion the Royal Oak proffers more appeal. The neatness of the 1972 model is sublime and this latest iteration of the Royal Oak shares this quality. The white gold screws featured on the bezel of the 1972 steel model, are now employed on the Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm. The contrast of the white gold screws against the pink gold octagonal bezel is magnificent. 

There is a wonderful reciprocity between brushed and polished surfaces. I especially like the bevelled, upper edge of the caseband. The slithers of polished metal shine beautifully adjacent the muted brushed surfaces. The watch is equipped with a screw locked crown, sporting the AP initials on its vertical flank.

An exhibition case back accentuates the skeletonisation and causes light to suffuse the movement.  Furthermore, the dorsal pane of sapphire crystal bestows wonderful front to rear views, allowing the wearer to see through the movement. 

There is a ubiquitous attention to detail which distinguishes this timepiece as special.

Additional movement details

I am conscious that by this stage some readers may feel overwhelmed by the numerous virtues of the Calibre 3132, however, there are still more attributes to discuss.

Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm

The second balance wheel features a facsimile of the upper balance bridge. Several screwheads sparkle, a characteristic accentuated by the chamfering of their rims. Several bridges are openworked, sporting exquisite anglage to heighten their lustre. The transmission wheel is openworked, beautifully finished and features two pristine screws atop its upper surface.

The Calibre 3132 is comprised of 245 parts, each refined to the highest order. The balance wheels oscillate with a frequency of 21,600 VpH (3Hz). The movement contains 38 jewels and the lone barrel provides 45 hours of autonomy.

Closing remarks

I have never been a poker player. I readily reveal my hand shortly after the cards are dealt. Likewise, despite my best efforts, I revealed my adoration for the Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm quite early in this review. 

Audemars Piguet has looked to the ultra-reliable Calibre 3120, adapted it, incorporated the ingenious ‘double balancier’ mechanism and openworked the movement, skilfully removing any extraneous material. However, one long sentence can never convey the protracted efforts expended by AP and its workforce in realising the Calibre 3132. Indeed, the expertise of this Maison, a company founded in 1875, is discernible when handling this paragon of fine watchmaking.

The ground-breaking Calibre 3132 is highly innovative and delivers superior precision and stability, something which great minds have strived to deliver for hundreds of years. However, despite the brilliance of this patented know-how, I suspect Audemars Piguet and other practitioners of haute horlogerie will continue their pursuit of improved accuracy. Indeed, as I have come to learn, the greatest watchmaking talent will never cease obsessing over the issue of precision.

Further reading

Technical specifications

  • Model: Audemars Piguet Royal Oak Double Balance Wheel Openworked 37mm
  • Reference: 15467OR.OO.1256OR.01
  • Case: 18-carat pink gold; diameter 37mm; height 10mm; sapphire crystal to front and case-back; water resistant to 5 ATM (50 metres).
  • Functions: Hours; minutes; central sweep seconds
  • Movement: Calibre 3132; self-winding movement; frequency 21,600 vph (3Hz); 38 jewels; power reserve = 45 hours; 245 parts.
  • Strap: 18-carat pink gold bracelet with AP folding clasp
  • Price: £60,700 (RRP as at 15.9.2018)

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