This 5550P Advanced Research is a fine example of how Patek Philippe, despite its long-standing historic legacy, aims to push forwards watchmaking through ingenuity, technological advances and bold aesthetic styling. Limited to 300 pieces, which are rumoured to all have been very quickly spoken for, the 5550P is as rare as it is unusual.

Pushing The Boundaries

Patek Philippe’s Advanced Research Program stems from the development of silicon components, for use in watchmaking. Despite technical advances, horology has traditionally relied on the same, basic materials for the last few centuries, with little evolution over the years. Alongside their more classic approach to horology, Patek Philippe has also attempted to innovate in the realm of material science and engineering. This is a long-standing approach from the manufacture, which has always sought to push the boundaries of accuracy and timekeeping, from early chronometer pocket watches to having an entire department dedicated to electronic timekeepers as early as the mid-20th century. 

The Advanced Research Program is one of the most recent steps in this journey. Following years of extensive research work at the Centre Suisse d’Electronique et Microtechnique (CSEM), Patek Philippe announced their first silicon component in 2005 – an escape wheel in a proprietary silicon dioxide formulation, known as Silinvar. This new material was used to rework the balance spring and the escape wheel, with Patek Philippe gradually implementing these innovations into three, successive annual calendar references: the 5250G, the 5350R and the 5450P.

The advantages of using silicon are well documented, despite the material’s reliance on technology. Through a combination of surface hardness and overall smoothness, mechanical components are able to interact without the use of oils, and can be fabricated with extreme precision. Though the material remains sensitive to temperature changes, it’s possible to produce formulations, such as Silinvar, which negate these effects. In fact, the Silinvar name is based on a contraction of silicon and invariable.

This Perpetual Calendar 5550P was intended to mark the culmination of this journey into silicon, integrating many of these innovations. The individual components tested with the preceding annual calendar references were integrated into the perpetual calendar, alongside further developments. In April 2011, former Patek Philippe president Philippe Stern announced that silicon balance springs would henceforth become the new standard for the brand, and gradually be added to future calibers.

The Design

The design of this 5550P is distinctly different to that of any other Patek Philippe perpetual calendar. The rose gold index markers and luminous-filled feuille hands create a visually striking contrast against the silvered, vertically brushed central section of the dial. The varied colours, indications, and luminous dots marking the hours gives the dial a bold appearance, while the vertical brushing plays with the light in appealing ways. In combination, the silvered colour and pronounced brushing give a distinctly modern appearance to one of Patek Philippe’s most traditional complications.

The dial has three registers, with the various functions neatly balanced out. The sub-dial at three o’clock shows the leap-year counter and the months, in a slightly concave sub-register, giving depth to the sharply-brushed, silvered dial. In a similar fashion, the months and day/night indicators are placed at nine o’clock. The gold moon and stars for the moon-phase are placed at six o’clock, with the days of the month around it, reminiscent of Patek Philippe’s earliest reference 3940 examples, where the moon and stars were also gold in colour.

This Patek Philippe 5550P features a nicely preserved 37.2 mm platinum case, with crisp hallmarks on the reverse side of the lugs. Like earlier examples from the Advanced Research series, it features a sapphire display caseback, with the addition of a cyclops magnifier to highlight the balance modifications.

The Movement

Powered by the caliber 240 Q Si movement, the 5550P features a Silicium escape wheel, anchor, hairspring and silicon balance wheel, forming the “Oscillomax” assembly. According to Patek Philippe, the increased efficiency of the 240 Q Si allows the calibre to have an increased power reserve of 70 hours, over the 48 hours found on the preceding calibre 240.

Closer look