The introduction of the Cubitus collection with its unconventional case shape in October 2024 did not go unnoticed.
Patek Philippe stated that the mission of the Cubitus collection is to "offer a new interpretation of the 'elegant, sporty' style" through a design where a square bezel gains rounded corners, "merging a square, circle, and octagon." Looking at the basic Cubitus models, the connection to the legendary Nautilus is obvious. This sparked skepticism about the design, as well as the fact that a round movement is housed in a square case. The complex model Patek Philippe Cubitus Perpetual Calendar Skeleton Ref. 5840P-001, presented at Watches and Wonders 2026, retained the case shape, but the dial no longer resembles the Nautilus thanks to its openwork 'shutter' design. The new caliber 28-28 Q SQU has a non-circular, special shape. Let's look through the 'shutters.'
Design and Case Features
The square case with rounded corners, integrated bracelet, and sporty character presents an alternative to the Nautilus. The first three large models focused on time and date, then in 2025, smaller precious metal versions appeared. At Watches and Wonders 2026, Patek Philippe took Cubitus to a new level by presenting the first large complicated model - Perpetual Calendar Skeleton ref. 5840P-001 (€176,700 / US$187,547 / CHF 150,000). This model noticeably distances itself from the Nautilus, primarily due to the skeletonized dial resembling shutters.
Review of Patek Philippe Cubitus Perpetual Calendar Skeleton ref. 5840P-001
A few months ago, after the debut of the first Cubitus models in 2024, I detailed the origin and goals of the collection. Cubitus was initially conceived as a new commercially successful project capable of diverting attention from the Nautilus. This was partly successful, but in the year of the 50th anniversary of the Nautilus, attention shifted back to it. Or not quite? At Watches and Wonders 2026, one of the most intriguing novelties was the Cubitus Perpetual Calendar Skeleton ref. 5840P-001 - with a horizontally open skeletonized dial that subtly reveals the complex QP mechanism with an unusual shape.
The new ref. 5840P-001 combines the bold architecture of the Cubitus case with a fully skeletonized perpetual calendar movement, specifically developed for the square case. Patek Philippe adapted the movement's construction to the case geometry, allowing for the most efficient use of space and emphasizing the collection's linear design.
Dimensions and Materials
The case diameter is 45 mm with a thickness of only 10 mm, despite the complex perpetual calendar mechanism inside. The case is made of two parts with lateral lugs, as in previous large Cubitus models. The alternation of polished and vertically satin-finished surfaces gives the case expressiveness despite the predominantly square silhouette. At the '6 o'clock' position, a diamond is embedded in the case, indicating the platinum execution. This model uses a baguette-cut diamond, which harmonizes better with the square shape than the traditional round stone.
Ref. 5840P-001 is a large model, but thanks to its thin case, it looks good on a large wrist. On a wrist with an 18 cm circumference, the watch seems a bit bulky and visually dominant, which can be perceived as excessive. However, on a larger wrist, the Cubitus fits comfortably, and its weight creates a sense of true luxury.
Dial Variations
The horizontally skeletonized blue dial evokes ambiguous but interesting impressions - it is original, expressive, and intriguing. This is a creative variation of a well-known dial theme. Patek Philippe uses laser-cut strips with blue PVD coating and horizontal brushing, creating a contrast with the predominantly monochrome movement. Horizontal lines reflect the mechanism's architecture, which we will discuss further.
The dial is equipped with applied white gold hour markers and baton hands with luminescent coating. Additional thin white gold hands indicate calendar functions: hours, minutes, small seconds, date, day of the week, month, leap year indicator, and moon phases.
Moon Phase Indication Features
The moon phase is a key function of this model. Instead of the traditional double window, ref. 5840P-001 offers a large single moon disk, completing a full revolution in 29.53 days. Multilayer mineral glass disks are used to create depth. The background is decorated with star engravings and blue lacquer, while a separate disk with the lunar surface image adds realism. This indication was previously used in limited anniversary editions, but for a regular model, this is new. It pairs excellently with the open dial, creating a focal point without adding traditional subdials.
Mechanism Behind the 'Shutters'
Behind the 'shutters' lies the new caliber 28-28 Q SQU - a square skeletonized perpetual calendar movement, based on the architecture of caliber 240 Q and specifically developed for Cubitus. Its design reveals complex perpetual calendar components. The movement consists of 313 parts and uses the well-known 48-month cam system, ensuring automatic accounting for the length of months and leap years.
Patek Philippe is known for impeccable movement finishing, and the 28-28 Q SQU is no exception, although the finishing here is restrained. Bridges, plates, and the micro-rotor are rhodium-plated, creating a predominantly monochrome appearance. Blue thermally hardened screws and the blue Calatrava cross add color accents. This modern, minimalist style emphasizes the model's innovativeness and its target audience. The movement can be seen through the transparent case back, as the view through the 'shutters' is limited and might cause disappointment.
Prospects for the Development of the Cubitus Collection
The emergence of Cubitus was initially perceived as an attempt to divert attention from the Nautilus, temporarily replacing it on the market and subsequently giving way. Similar to other Patek models, such as Neptune. However, Cubitus is not going into the shadows. In the anniversary year of the Nautilus, Cubitus acted as a spectacular and interesting 'warm-up' before the main event. Perpetual Calendar Skeleton ref. 5840P-001 boldly takes the collection in a new design direction, heralding bold and innovative solutions.
If Patek continues to use the square case for new movements, this guarantees interesting technical solutions, as the 28-28 Q SQU caliber has already proven. In the future, synergy between the case and movement may strengthen, especially if the Advanced Research department, created in 2005, gets more opportunities to implement innovations.
Conclusion and Questions for Experts
The only thing that raises questions is the use of straps with contrasting stitching. On the ref. 5840P-001 model, this is a blue Cordura strap with texture and cream stitching. Despite the platinum buckle engraved with Cubitus, the stitching distracts attention and seems out of place for high-class watches. Perhaps this is a subjective opinion, but such an element looks like a 'cheap' trick.
What do you think about this complex Cubitus complication? Has your attitude towards the collection changed in general? What other complications, in your opinion, would suit the Cubitus design? For example, a mono-counter chronograph might fit well in style. Share your opinion in the comments.