Looking Through The Blinds: A Peek At The Patek Philippe Cubitus Perpetual Calendar Skeleton Ref. 5840P-001
The introduction of the distinctly different-shaped Cubitus collection in October 2024 didn’t go unnoticed. Patek Philippe stated that the Cubitus collection’s mission is “to offer a new reinterpretation of the ‘elegant, sporty’ style” through a design in which the square bezel adopts rounded corners, “blending the square, the circle, and the octagon.” When you look at the basic Cubitus models, the link to the mighty Nautilus is obvious. That’s also what fueled much of the skepticism regarding the design. That and the fact that the square case housed a round movement. The complicated Patek Philippe Cubitus Perpetual Calendar Skeleton Ref. 5840P-001, which debuted during Watches and Wonders 2026, might still have the same case shape, but the dial is no longer so Nautilus-like thanks to its open-worked “blinds.” And the new caliber 28-28 Q SQU is not round but shaped. Let’s peek through the blinds.
The square case with rounded corners, an integrated bracelet, and a sporty character. Also, an alternative to the Nautilus. The first three large references focused on time and date, followed by smaller precious-metal versions in 2025. Now, at Watches and Wonders 2026, Patek Philippe takes the Cubitus into more complicated territory with its first grand complication. Meet the Cubitus Perpetual Calendar Skeleton ref. 5840P-001 (€176,700 / US$187,547 / CHF 150,000). This is a watch that, more than before, distances itself from the Nautilus, if only because of its open-worked dial that reminds me ever so slightly of Luxaflex…
A peek at the Patek Philippe Cubitus Perpetual Calendar Skeleton ref. 5840P-001
I wrote about the Cubitus a couple of months after the first watches debuted in 2024. I tried to explain how the collection came about and what its intentions were. Well, the idea was to have a new commercial golden boy that could draw attention away from the Nautilus. It did partially, but this year, with that model celebrating its 50th anniversary, it’s all about the Nautilus again. Or is it? During Watches and Wonders 2026, one of the most intriguing and surprising novelties was the Cubitus Perpetual Calendar Skeleton ref. 5840P-001. It must be the horizontally open-worked dial that, ever so shyly, allows you a glimpse of a skeletonized, shaped, complicated QP movement.
The new ref. 5840P-001 combines the bold Cubitus case architecture with a fully skeletonized perpetual calendar movement developed specifically for the square case. Patek acted like Patek when they adapted the movement architecture to suit the watch’s geometry. The result is a movement layout that makes the most of the available space while emphasizing the collection’s linear design language.
Measures and materials
The case measures 45mm across and is just 10mm thick despite housing a complicated QP movement. As with the earlier large Cubitus models, it uses a two-part construction with lateral lugs. The alternating polished and vertically satin-brushed surfaces give the case some visual definition despite its predominantly square outline. At 6 o’clock, the usual diamond set into the case signals that the case is made of platinum. In this instance, Patek Philippe opts for a baguette-cut diamond, which suits the squarish look better than the typical round diamond you would “normally” get.
The ref. 5840P-001 is a large watch. But because of its slender 10mm thickness, it also blends in rather nicely when you’re lucky enough to have a large wrist. On my 18cm circumference wrist, it is slightly too big to my liking. The watch takes up a bit too much space, and because its looks are so prominent, it’s visual overkill. Having said that, on a bigger wrist, the new complicated Cubitus will nestle quite comfortably. And noticeably because of its hefty weight, which some consider the ultimate feeling of watch luxury.
Variations on a dial theme
Say what you will about the horizontally open-worked blue dial, it sure is original, striking, and intriguing. It’s also a creative variation on the famous existing dial theme. Patek uses laser-cut strips that are finished with a blue PVD treatment and horizontal brushing. They provide some contrast to the largely monochromatic movement, and horizontal lines also echo the architecture of the movement below, but more on that technical masterpiece later on. The dial features applied white-gold hour markers and baton hands filled with luminescent material for the time display. Additional slender white-gold hands indicate the calendar functions. The display includes the hours, minutes, and small seconds, as well as the date, day, month, leap-year indication, and moon phases.
The moon-phase display is a function that dominates the watch. Instead of the traditional dual-moon aperture, the ref. 5840P-001 features a large single moon. The display completes one rotation every 29.53 days and uses layered mineral-glass disks to create a sense of depth. Engraved stars and blue varnish form the background, while a separately structured moon disk depicts the lunar surface. This moon could be spotted in limited anniversary pieces before, but this is the first time the large single-moon display appears in a regular-production model. It also suits the open-worked dial very well. Your eyes don’t slip through the horizontal openings immediately, but instead, the prominent moon adds a focal point. And it does so without adding another conventional sub-dial to an already quite busy watch face.
Behind the “blinds”
Behind the “blinds” beats the new caliber 28-28 Q SQU. This square, skeletonized perpetual calendar movement is derived from the architecture of the caliber 240 Q and is a special development for this complicated Cubitus. Its skeletonized construction opens the mechanism and reveals its complicated “secrets,” including the perpetual calendar components. The caliber comprises 313 components and uses the familiar 48-month cam system found in perpetual calendars based on the 240 architecture. It goes without saying that the movement automatically accounts for the different lengths of the months and the leap-year cycle.
Patek Philippe is famous for its exquisite movement finishing, and the caliber 28-28 Q SQU is further proof of that, yet it’s also surprising. That’s because Patek has kept the finishing deliberately restrained. The bridges, plates, and micro-rotor are rhodium-plated, creating a largely monochromatic appearance. Heat-blued screws provide small flashes of color, as does the blue Calatrava cross on the movement. The result is a complicated caliber that presents its beauty in a more contemporary, casual fashion. It suits the Cubitus and, most likely, its target audience. It is a good thing the movement can be admired through the display case back, because only seeing it through the “blinds” would prove incredibly frustrating and in time, infuriating.
Where is the Cubitus going?
When the Cubitus first appeared, it looked to me as if it wanted to take the attention of the Nautilus by looking like it. It was going to take the pressure off the Nautilus by replacing it for a while, sell like hot cakes, and then slowly fade away as some watches do. Even Pateks. Do you still remember the Neptune? Exactly. But the Cubitus hasn’t sailed into the sunset yet. When the celebrating Nautilus took center stage, the Cubitus was the opening act. And that opening act was, in a way, more spectacular and interesting than the headliner. The Cubitus Perpetual Calendar Skeleton ref. 5840P-001 adventurously takes the collection in a design direction that foreshadows daring, novel designs. The Cubitus could be a platform for innovation in both design and movement technology.
When Patek continues to use the square case to introduce new movements, that same case shape means those movements will be interesting, as the caliber 28-28 Q SQU already proves. In the future, the symbiosis between case and movement could be taken even further. I hope this happens because it could mark the start of a new era for Patek, in which the Advanced Research department, established in 2005, gains more space and opportunities to showcase its innovations and inventions.
What I certainly don’t hope is that Patek continues to outfit every watch with a strap featuring contrast stitching. It’s a minor gripe, but I can’t stop looking at the ref. 5840P-001’s navy-blue Cordura strap with a textile pattern and contrasting cream stitching. No matter the platinum folding clasp with three independent catches and an engraving referencing the Cubitus collection, it’s the contrast stitching that catches my eye. It’s a “cheap” trick to add detail to a watch, unfitting a high-end watchmaker like Patek, but maybe I’m the only one who’s put off by it.
What do you think of this grand complication, Cubitus? Is this a reference that changes your opinion on the Cubitus collection as a whole? Are there any other complications you think would fit nicely in the Cubitus design language? A mono-counter chronograph design could work for a Cubitus, don’t you think? Let me know your thoughts in the comments section below.
