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The Audemars Piguet Royal Oak Perpetual Calendar In Titanium

Jack Forster6 Min ReadAug 24 2023

Certain complications become identified with particular brands for a reason. Of the great classic watch brands in Switzerland, probably the two most strongly identified with the perpetual calendar are Patek Philippe and Audemars Piguet. This is not to say that other companies have not made outstanding perpetual calendars – Jaeger-LeCoultre, for instance, has made exemplary perpetuals both under its own name and as a supplier of movements to clients. Breguet may well have made the first perpetual calendar designed specifically for a wristwatch (Patek made the first wristwatch perpetual although the movement had originally been designed for a ladies’ pendant watch). IWC created the first perpetual calendar which could be set entirely from the crown, with the movement designed by Kurt Klaus.

Zoom InAP 5516, with leap year indication and month indication at 6:00. Image, AP archives.

But for continuous production across a continuous history of manufacturing, AP and Patek are hard to beat. Patek made its first series produced perpetuals in 1941. Audemars Piguet made its first perpetual calendar watches in 1955 – the reference 5516, which was the first perpetual calendar with a leap year display – and since then, they have produced some of the most beautiful and interesting perpetual calendar wristwatches in the world, often in Royal Oak cases.

The first Royal Oak perpetual calendars used a movement which had originally been sold in a non-Royal Oak watch – the reference 5548, which as the first automatic ultra-thin perpetual, was another milestone for watchmaking history and for Audemars Piguet. The perpetual calendar module was constructed on the same base movement AP used for the Jumbo Royal Oak: the ultra-thin caliber 2121. The base movement, combined with a perpetual calendar module designed in-house by AP and made for them by Dubois Depraz, was only 3.95mm thick. The 2121 is 3.05mm thick, however that’s with the date wheel; the no-date 2120 is only 2.95mm thick, so removing the date wheel from the movement gives you some extra space to work with and so the 3.95mm thick 2120-2800 was born. In 2015, AP made its first major update to the movement by adding a day of the week indication; the caliber, renamed the cal. 5134, grew slightly in thickness – to 4.31mm – and that movement is the one ticking in the Royal Oak Perpetual Calendar Titanium China Exclusive we’re featuring for this A Watch A Week.

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This particular version of the Royal Oak perpetual calendar is no longer in AP’s catalog, which currently features a total of 12 Royal Oak perpetuals – two of these are grand complications, which don’t use the caliber 5134.

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The reference 26609TI.OO.1220TI.01 (AP has some of the longest reference numbers you may ever hope to see) is in a lot of respects an absolutely classic take on the Royal Oak perpetual. The first Royal Oak perpetual calendar came out in 1983 as the reference 5554, and it had a very simple dial: four equidistant, equally sized subdials showing the month, date, phase of the moon, and day of the week. The first Royal Oak perpetuals with non-smooth dials showed up in the late 1980s and early 1990s.

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As is so often true with Audemars Piguet, however, much of the horological interest of the watch, is in the movement. The caliber 2120/1 was discontinued for the Royal Oak, by AP, for the 50th anniversary of the brand, in 2022 (which seems like an odd way to celebrate) and the Jumbo 16202 how houses the caliber 7121, which has a completely different movement architecture. The 7121 is I’m sure more robust, almost certainly more precise, and if it is not much easier to service than the 2121 I will eat my hat, but the 2121 has on its side, a visually very compelling combination of fine finishing as well as real mechanical beauty in the arrangement of its components. No longer available in standard Royal Oak models, the 2120/1 is only available from AP as the base caliber for its perpetual calendars.

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The distinguishing feature of the 2120/1 (aside from the non-quickset date in the 2121, which to be fair, was a little irksome to some owners – a quickset date in a modern watch is not too much to ask) aside from its very slim dimensions, is the mounting system for the automatic winding weight. As you can see there is very little of the rotor that actually sits above the level of the movement plate. Most of the mass is distributed to the periphery which of course is true of just about every selfwinding movement rotor out there – it makes for a more efficient winding system. However in the 2120/1 as seen above, the massive peripheral section is actually mostly below the upper level of the movement plate. The rotor, except for the peripheral mass, is extremely thin and to help support it and keep it from making contact with the movement plate, there is an ingenious system of ruby rollers hidden under the outer edge of the rotor, whose mountings are only visible if you decase the movement.

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The rotor is secured by a clip to a beryllium bronze post, and you’ll notice that the balance spring is flat – for a movement with a freesprung balance like this one, and with such a wealth of beautiful detail, you might expect an overcoil balance spring but that would have added to the thickness of the watch. Power reserve for the base caliber is 40 hours and the perpetual calendar 5134 maintains the same power reserve.

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It’s an exquisite piece of work and the base caliber is still the thinnest full rotor perpetual calendar in the world. The 2120/1 was made by Jaeger-LeCoultre as the caliber 920 but interestingly enough, the brand never used it in its own watches. Patek Philippe, Audemars Piguet, and Vacheron Constantin all made use of it but it is no longer available as a standalone movement from any of those brands although Vacheron still uses it, as the caliber 1120, in its Overseas Perpetual Calendars.

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The constant exposure of the Royal Oak has done a lot to outshine some of the horological importance of what is arguably fine watchmaking’s most recognizable design. Not all Royal Oaks are created equal however in this watch, you have what in my opinion is one of the finest perpetual calendars ever made. It has history on its side, it represents a vanishing devotion to craftsmanship in fine watchmaking, and it is part of a lineage of some of the most interesting and important perpetual calendars ever made, going all the way back to the 1978 launch of the 5548. In terms of everything that made Swiss high-end watchmaking capable of surviving the Quartz Crisis, there are few watches comparable. The combination of a classic movement with an absolutely classic design means that the Royal Oak Perpetual Ultra Thin in titanium offers, not hand-waving marketing copy about Heritage and Craftsmanship, but a double shot, no chaser, of the real thing.