Over the last few years, the Audemars Piguet Royal Oak Perpetual Calendar has once again become a mainstay of the Audemars Piguet collection. In fact, some of AP’s hottest watches since they revamped the RO QP in late 2015 have been variations on this theme (of course there is also the award-winning Royal Oak Selfwinding Perpetual Calendar Ultra-Thin – but that’s a different thing entirely). Today we’re getting a limited edition take on the standard Audemars Piguet Royal Oak Perpetual Calendar , made exclusively for the Chinese market. Audemars Piguet has gone way beyond the slightly predictable red accents on the week indicator hand and the supplied rubber strap, making the full case and bracelet in lightweight titanium. The whole watch, with the bracelet, weighs in at just 104 grams. This is the first time that a Royal Oak Perpetual Calendar has ever been produced in full titanium, which is definitely nothing to scoff at. (Previous RO QP models have featured a combination titanium/platinum construction, with the bezel and center bracelet links made in the precious metal.)

This watch is limited to just 88 numbered pieces (eight being a lucky number in Chinese culture) and they are only available at Audemars Piguet boutiques in mainland China. No reason to pull punches here – I really dig this watch. The sleek grey dial is really handsome, the red accents aren’t too over the top (though I don’t think I’d personally wear the red rubber strap much), and the titanium construction sounds really appealing. Some of my favorite AP watches of all time are the titanium/platinum combination models, so I can only imagine how comfortable this one will be on the wrist.
The fact that it’s only available in-boutique and in mainland China means that there are definitely going to be a lot of disappointed people who never even get to see one of these up close (me likely among them), but I appreciate that AP did something actually special for this instead of just changing up a dial color or adding an engraving to the back.

I’ve enjoyed seeing AP embrace the Royal Oak QP as a platform for creativity and innovation these last few years. In the last 12 months, we’ve gotten a sleek all-platinum version, a white ceramic version with a stunning blue dial, and a skeletonized black ceramic version (which is a follow-up to the original black ceramic QP that broke the watch internet during SIHH 2017). It’s not that long ago that every week seemed to bring us a new limited edition Offshore with some crazy color combination or a weird spattering of gemstones – this new direction is much more my speed and I love it when AP combines their old-school watchmaking chops with the Royal Oak. It’s a proven, winning formula.
One interesting facet to this story is that Audemars Piguet says that this watch was developed in collaboration with collector Austen Chu (who you probably know as @horoloupe on Instagram). We’re obviously no stranger here at Audemars Piguet Royal Oak Perpetual Calendar to working with watch brands on limited editions, but it’s really fascinating to see a major brand work with an individual collector instead of a retailer or publication. I don’t think we’ll be seeing a ton of this, but it’s definitely something to keep an eye on.

Considering the investment that it must have taken from AP to make this full titanium construction possible (you can’t make titanium components using the same tools and techniques that you use for steel or gold components), I’ll be very curious to see if we start getting more titanium editions, either limited or mainline, in the near future.
Today we are talking about a topic that typically gets overlooked. How to set your watch is as important as knowing your watch from A to Z. Setting a perpetual calendar is never an easy process, even when the watch is equipped with one or two correctors only, or if everything can be set via the crown —like on many of the Jaeger-LeCoultre Perpetual Calendars. When it comes to the Audemars Piguet Royal Oak Perpetual Calendar ref. 26574 it is better to be safe than sorry. Setting this perpetual calendar is not an easy process and the risk of damaging the mechanism is always present. Our advice is to always, always follow the manufacturer’s instructions and do everything in the right order. While Audemars Piguet offers an online interactive guide that is very useful and walks you through the whole process step-by-step with 14 steps, sometimes it is easier to follow a shorter/quicker guide —not necessarily interactive— that has been put together by someone else that has digested Audemars Piguet’s guide many times.
While the interactive guide is amazing, sometimes we struggle to have to follow 14 interactive steps. That’s exactly why we bring you this guide with six steps that have clear visuals and which accurately outline the necessary steps in a more simple and straight to the point manner —of course, all based on AP’s instructions.

By no means, our guide is intended to replace AP’s instructions and we take no responsibility for any damage caused to the mechanism on your watch for improperly setting it. We provide this guide as a convenience to you and you follow it at your own risk.

Always avoid correcting the date, month, or lunar cycle in the afternoon or evening. Similarly, avoid manipulating the annual or perpetual calendar outside of the time ranges recommended in the watch manual.
Ultra-thin watchmaking makes headlines, all right, but breaking into it can be a tough game. First of all, it requires a lot of expertise – not for nothing is the genre sometimes referred to as its own separate form of complicated watchmaking, on a par with crafting rattrapante chronographs or minute repeaters. It’s not just a question of making everything flatter, although that alone creates challenges. With clearances between components reduced to almost nothing, errors in alignment of components which would be trivial in a thicker movement or watch, can become deal-breakers. Components are also more delicate (and in watchmaking they’re often pretty delicate to start with) and require a great deal more care in handling during the assembly process. The new Audemars Piguet Royal Oak Selfwinding Perpetual Calendar Ultra-Thin, is an exciting new entrant in the world of ultra-thin watchmaking – both for its seductive aesthetics, and for its use of some very original solutions to basic problems in ultra-thin watchmaking. To really have a shot at making something attention-getting in ultra-thin, or extra-flat watchmaking (the two terms, by the way, are generally used interchangeably, although “ultra-thin” to my ear has always seemed to have a little more va-voom to it) you have to start constructing the movement differently from how you’d construct a conventional watch movement. Over the last five hundred years of watchmaking there have been a couple of especially significant moments in slimming down the watch. The first of these was the development of escapements that allowed thinner construction – first, the cylinder escapement, and then the lever escapement, made it possible to make much flatter watches than you could with the verge escapement (the first known escapement used in watch and clockmaking in Europe).

Another essential development was the evolution of the so-called Lépine caliber, which was developed by Jean-Antoine Lépine in the 18th century, and which did away with the bulky but then-ubiquitous fusée. This allowed the balance to be placed on the same plane as the rest of the going train, and combined with the use of now-standard bridgework, rather than the earlier pillar-and-plate construction, made it possible to make really flat watches for the first time.
Audemars Piguet has had a long history of making extra-flat watches, including a “knife” pocket watch caliber, in 1921, that was a mere 1.32mm thick, as well as its production of time-only watches, post-World War II, based on 13-ligne movements provided as blanks, by Valjoux. Of course, its release in 1967 of the 2.45mm-thick caliber 2120, set a record which stands to this day. One of its proudest moments in ultra-thin watchmaking, however, was in 1986, when it launched its caliber 2870 tourbillon. This remarkable watch, reference 25643, was until very recently the flattest automatic tourbillon in the world, at only 4.8mm thick, and made use of a revolutionary case construction, in which the back of the watch case did double duty as the upper movement plate as well.

Records, it’s said, were made to be broken and after a long and apparently unassailable reign, the right to call a watch the flattest tourbillon wristwatch in the world, passed to Bulgari with the announcement of the Octo Finissimo Tourbillon Automatic, in 2018. However, by then Audemars Piguet was already well along in the development of a watch that would reassert the company’s expertise in ultra-thin watchmaking: the Royal Oak Selfwinding Perpetual Calendar Ultra-Thin.
The Royal Oak Selfwinding Perpetual Calendar Ultra-Thin had a start in life as something somewhat different than the final production model – when Jon Bues reported its introduction last January, at the SIHH, it was introduced in a solid platinum case, with a brushed bezel and classic Royal Oak tapisserie dial, and while an impressive technical achievement, it also felt very much like a prototype, especially when measured against the production watch. Jon noted that for all its remarkable dimensions (41mm x 6.3mm, which are also the dimensions of the production watch) it felt a bit heavy, which after all is no surprise in a solid platinum watch on a solid platinum bracelet, no matter how flat).
The production model has a simple, vertically brushed matte blue dial (the brushing is very subtle) with barely-sunken subdials for the date indications. The moonphase is still present as well. The subdials have been slightly enlarged as well, and the changes to the dial, and switch to a plain mirror polished bezel, improves legibility significantly, and gives the watch a much more refined and restrained aspect – it just feels more like an ultra-thin watch, even though the dimensions are identical to those of the concept watch. Instead of solid platinum, the majority of its construction is now titanium, which gives the watch a reduction in heft commensurate with its svelte profile. The case and bracelet are titanium, with a platinum bezel and platinum center links. The overall impact of an ultra-thin watch can be judged by several measures, but it never hurts when one of the reactions that someone seeing and holding it for the first time has, is a slight sense of disbelief that the watch exists at all. This really is a bit of a shocking watch, and all the more so in that it whispers its excellence rather than shouting it. This is, to put things in context a bit, not the first Royal Oak Perpetual Calendar, of course. There is for example the very beautiful Royal Oak Perpetual Calendar 41mm, which on the face of it, has much in common with the Ultra-Thin – including the fact that the movement in both cases, is based on the Audemars Piguet ultra-thin caliber 2120, so you would expect the overall watch dimensions to coincide somewhat closely. In fact, the Audemars Piguet Royal Oak Perpetual Calendar 41mm is 41mm in diameter but also 9.5mm thick, versus 6.3mm thick for the new Ultra-Thin. This is still, by any measure, a pleasantly flat version of a perpetual calendar, with an extremely refined movement and one which most lovers of high end high complications would enjoy immensely, the Ultra-Thin notwithstanding. It does give you an inkling of how much the movement has been re-thought and re-engineered, however, that while the Ultra-Thin is a hair wider (one millimeter exactly) it is also over 3mm thinner; 3.20mm thinner, to be exact, which means that AP found a way to shave almost a third off the thickness of what was a pretty darned thin watch to begin with.
Although the view through the caseback looks at first glance very much like a standard caliber 2120, the new perpetual calendar caliber 5133 is very different from Audemars Piguet’s standard 2120-based perpetual calendar. That movement, the caliber 5134, is essentially the 2120, with the addition of a perpetual calendar plate that sits on top of the dial side of the main movement plate. In the 5134, the perpetual calendar mechanism under the dial (or cadrature, as under-the-dial work is called) is a classically constructed perpetual calendar, with the various levers, gears, and jumper springs that make up the perpetual calendar mechanism existing in three distinct layers. This is in addition to the actual timekeeping mechanism, including the mainspring barrel, going train, escapement and balance on the other side of the movement mainplate, and the full rotor automatic winding weight. The base caliber 2120 is 2.45mm thick, and the 5134 comes in at 4.31mm, so the perpetual calendar work in the 5134 adds a mere 1.86mm in thickness to the movement. Having the caliber 2120 as a starting point means working with a movement that is already a specialized piece of ultra-thin watchmaking. It was upon its debut in 1967, the thinnest automatic movement in the world and although there are now thinner self-winding watch movements, it remains the thinnest full-rotor automatic movement, which is a remarkable track record. The 2120’s rotor is designed to have most of its mass on the rotor’s edge, which is supported by a beryllium ring that runs on ruby rollers. The automatic winding train, which in other movements is often on a separate bridge above the going train, is on the same level as the going train in the 2120, and the barrel is a so-called “hanging” barrel, meaning that there is no upper barrel bridge–it’s supported by a single point of attachment, on the movement mainplate. The caliber 5133 goes the 5134 one better, by taking the classic 3 level construction of the perpetual calendar works, and compressing everything into a single layer. This single layer’s effect on the movement’s thickness is further reduced by placing the components into shallow recesses milled out of the dial side of the mainplate itself, and, as well, using the dial as part of the supporting structure for the perpetual calendar works – this is reminiscent of the use of the caseback for the same purpose, by AP, in the 1986 caliber 2870.
There are some other notable technical innovations as well, which may sound minor, but which represent significant changes from a typical perpetual calendar mechanism. A perpetual calendar, as most watch enthusiasts know, always displays the correct date, even at the end of February in a Leap Year (in a simple calendar watch, for months shorter than 31 days, you have to manually correct the date at the end of the month). The way Audemars Piguet Royal Oak Perpetual Calendar usually keep track of the length of any given month in the calendar, is via a special program disk, which has 12 steps cut into its edge, the depth of which corresponds to the length of each month. In a wristwatch, the disk has twelve of these steps. A lever that determines how many days the calendar should jump at the end of each month, drops into each of these steps in succession and the deeper the step, the greater number of days the calendar jumps forward. The deepest step is for February, when the calendar has to jump from the 28th, to the first of March).

Once every four years – the Leap Year – an extra day is added to February, which keeps the Gregorian calendar correctly aligned with the Earth’s actual position in its orbit. This means the watch has to jump the date from the 29th, not the 28th, of February. Usually this is handled by means of a special four-faced cam that rotates once every four years, which sits on the underside of the program disk. AP did away with the cam as a height-saving measure, and instead, uses a program wheel with a full 48 steps in its edge, instead of the usual 12, for a full Leap-Year cycle. The steps are also different from those found in a conventional perpetual calendar – they’re narrow, curved slots, which both allows 48 steps to fit inside a wristwatch movement, and provides smoother engagement for the tip of the date-change lever.There are several other interesting innovations as well. The program wheel is usually indexed by a separate month-change cam; in the caliber 5133, this function is performed by a special tooth on the date disk which (as you might guess) makes one full rotation per month. At the end of the month, this tooth engages with a tooth on the edge of the program wheel, indexing it to the next month. The flattening of all the perpetual calendar components into a single layer, means that the 5133 is a bit wider than the 5134 and 2120 – 32mm, vs 29mm, but it seems a small price to pay for a new world’s record which will be difficult in the extreme to overturn, especially if competitors want to offer a full-rotor movement. You’ll recall that the 5134 adds only 1.86mm in height to the base caliber 2120 – the 5133, on the other hand, at 2.89mm thick, adds just 0.44 mm to the height of the original caliber 2120. By any measure this is a remarkable achievement for Audemars Piguet, and it’s a much needed reminder to enthusiasts – and maybe a reminder to AP itself – just how rich its history is not only in technical watchmaking, but in a very elevated, almost unique form of technical watchmaking. The Royal Oak Selfwinding Perpetual Calendar Ultra-Thin is watchmaking at its most compelling.
art of the magic of traditional watchmaking is its transformation of mundane materials into mechanical art – it relies for the most part, and for most of its history has relied, on just a few relatively simple things; things like brass, and gold, and steel. This watch feels very much a part of that tradition; there are a few exotic elements (the balance spring alloy for one, that beryllium rail for the rotor for another) but it’s most watchmaking of the old school, and it shows just how much potential remains in taking a long, hard look at tradition, discarding received wisdom, and challenging yourself to take a fresh approach.