Patek Philippe 5951P Perpetual Calendar Split-Seconds Chronograph Review

The most complex integrated movement created by Patek Philippe, featured in the reference 5951P, doesn’t rely only on tradition. While it combines all of the maison’s experience in perpetual calendars and an integrated moonphase, it also adds a split-seconds chronograph that’s operated by a single button in the crown, all within a tonneau-shaped case that marks a significant visual departure from the time-tested norm of high-end Patek Philippe watchmaking. And it’s even more compelling because of it. 

Patek Philippe debuted their first fully in-house chronograph in 2005, the hand-wound caliber 27-525, which was the world’s thinnest split-seconds chronograph movement at only 5.25mm in thickness. Its start/stop/reset functions are all contained within a single pusher integrated into the crown, while a rectangular pusher above it controls the split-seconds mechanism. Reference 5951P debuted in 2010, adding a perpetual calendar to the movement’s functions. The resulting CHR 27-525 PS Q movement is still an ultra-thin masterpiece at just 7.3mm thick, and it’s even more impressive to consider that its platinum case measures just 37mm in diameter, which is about as compact as a Patek perpetual calendar can be. 

This particular variant features a “reverse panda” color scheme, with its subdials and lower date ring at the six o’clock position in white, set against matte black. More traditional-looking examples of the ref. 5951P feature Breguet numerals ringing a glossy black dial, while this more contemporary-looking example features baton indices in white gold. Unusually, the hands for all three subdials are all different colors: white for the date, black for the subsidiary seconds at nine o’clock, and red for the central sweep chronograph and rattrapante hands and the 60-minute counter at three o’clock, providing a colorful balance to the blue-disc moonphase at the top of the dial at twelve o’clock. On the back, it would be a shame to hide such mechanical complexity, and an exhibition case shows off wonderfully finished details such as the thin S-shaped clutch lever and dark gray components. For those who wish to keep the movement’s beauty to themselves, a solid platinum caseback is included as well.

The movement and exhibition caseback are framed by a case shape that’s commonly known as a “TV dial.” Tall, assertive lugs bow outwards to form the simple shape of the case’s sides, which is polished throughout without any contrasting brushed shapes or elements, matching the subtly octagonal crystal and breezing past the pinholes that allow the perpetual calendar setting on the left-hand side. TV dials like this were big in the 1970s, when watchmakers were inspired by the shape of the future; in this ref. 5951P, Patek Philippe combines such retrofuturism with the masterful complications that it does best.