Patek Philippe Ref. 5951P – Split-Seconds Monopusher Chronograph with Perpetual Calendar with Platinum Case and Black Dial

Legendary Swiss watch brand Patek Philippe presents new complication-Ref. 5951P, the thinnest split-seconds monopusher chronograph ever made with a perpetual calendar.

It is absolutely legitimate to assign Patek Philippe’s split-seconds or rattrapante chronographs to the category of Grand Complications which also includes minute repeaters, tourbillons, and particularly elaborate calendar mechanisms as well as astronomical functions.

The Ref. 5951P, which combines a split-seconds chronograph with a perpetual calendar, will therefore no doubt rank among the most exciting debuts at this year’s Baselworld show. The specifications imposed another challenge: the movement was to be as thin as possible.

Patek Philippe Split-seconds Monopusher Chronograph with Perpetual Calendar, Ref. 5951P

Patek Philippe’s CHR 27-525 PS basic caliber is already the thinnest column-wheel-controlled split-seconds chronograph movement, so it seemed appropriate that the perpetual calendar cadrature should be similarly discreet. The task was compounded by the fact that the movement has a diameter of only 27,3 mm.

Nonetheless, the workshops succeeded in designing a calendar module with a day/night display that indicates the date, day, month, leap year cycle, and moon phase yet measures only 2.05 mm from top to bottom. Together with the basic movement, this adds up to an overall height of just 7.3 mm, making the new Ref. 5951P the thinnest rattrapante chronograph with perpetual calendar ever crafted by Patek Philippe.

The outcome of this innovation is a perpetual calendar with a moon-phase display comprising 148 individual parts in a cadrature with a diameter of just 27,3 mm and a height of 2.05 mm. It controls a moon-phase display and an analog date as well as the day, the month, the day/night indication and the leap-year cycle in apertures.

This module with a perpetual calendar was developed expressly for the CHR 27-525 PS split-seconds chronograph movement launched in 2005 and now joins it in the new caliber CHR 27-525 PS Q. Due to its extreme complexity, this caliber is exclusively hand-crafted one by one.

Among its special features is the 60-minute chronograph counter driven via the cannon pinion, an ingenious construction that contributes significantly to the ultra-thin silhouette of the movement. Of course, the chronograph wheels of the caliber also have Patek Philippe’s patented tooth profiles that improve its efficiency, reduce friction, and boost functional reliability when the chronograph is engaged.

Its Gyromax balance wheel is fitted with a Breguet balance spring that breathes with a frequency of 21,600 semi-oscillations per hour (3 hertz). The chronograph’s start, stop, and reset commands are activated by a single in-crown pusher. Lap times are stopped with a rectangular push piece at 2 o’clock.

Patek Philippe Split-seconds Monopusher Chronograph with Perpetual Calendar Platinum, Ref. 5951P
The design of the dial also proved to be a challenge. In a relatively small area, it delivers no fewer than 12 indications: three hands for standard time in hours, minutes, and seconds, three hands for the splitseconds chronograph functions, plus the day, month, date, leap-year cycle, moon phase, and day/night indication.

Despite the density of information that it provides, the sporty black dial of the Ref. 5951P is quickly and easily readable. The moon-phase display in the gracefully curved aperture at 12 o’clock deviates from the true lunar cycle by only one day in 122 years. Standard time is indicated with leaf-shaped white-gold hands and applied baton-style hour markers. For contrast, short-time measurements are tracked with red hands.

The fine tips of the chronograph and rattrapante hands follow a scale that precisely emulates the contour of the cushion shaped bezel. The subdial for the analog date is positioned at 6 o’clock flanked by round apertures for the day/night indicator and for the leap-year display.

For once, the years are indicated with Arabic rather than Roman numerals, emphasizing the modern, masculine style of this split-seconds chronograph. The days of the week are displayed in an aperture between the date scale and the seconds subdial, whereas the month aperture is symmetrically positioned on the 60-minute counter side.

With such a clear and aesthetic time and calendar data presentation, Patek Philippe demonstrates yet again that it tolerates no compromises, neither in functionality nor in design.

Patek Philippe 5951P
The Ref. 5951P has been endowed with a cushion shaped platinum case to accommodate its ultra-thin movement. It is reminiscent of the famous art-deco watches for which the manufacture received rave reviews in the 1920s and 1930s.

The rectangular rattrapante pusher in the side of the case at 2 o’clock – it is used to stop lap times – was also inspired by historic models. Next to it is the knurled crown which contains the pusher that controls the chronograph. The sapphire crystal glass duplicates the cushion shape of the case, a square form with curved sides.

The sapphire-crystal insert in the snap back has the same contour. It is a show window on a magnificent movement, revealing many hand-finished components, the elaborate rattrapante mechanism, and the rhythmic beat of the Gyromax balance wheel. It is a sight that will never bore the true watch enthusiast even though the ballet repeats itself infinitely.

Technical details

Model: Patek Philippe Split-seconds Monopusher Chronograph with Perpetual Calendar, Ref. 5951P

Caliber CHR 27-525 PS Q
Manually wound mechanical movement, split-seconds monopusher chronograph with column-wheel control, chronograph and rattrapante hands, 60-minute counter, and seconds subdial. Perpetual calendar with day, month, leap year, and day/night indication in apertures and analog date. Moon phase.
Diameter: 27.30 mm
Height: 7.30 mm
Number of parts: 400
Number of jewels: 27
Power reserve: 48 hours
Balance: 2-arm Gyromax with 8 poising weights
Frequency: 21,600 semi-oscillations/hour (3 Hz)
Balance spring: Breguet

Two-position crown:
– Pulled out: To set the time
– Pushed in: To wind the watch
– Chronograph start, stop, and reset with in-crown push piece
– Rattrapante start/stop push piece at 2 o’clock

Center hour and minute hands
Sweep chronograph and rattrapante hands

– Day and day/night indication between 7 and 8 o’clock
– Month in black and leap year in red between 4 and 5 o’clock
– Moon phase at 12 o’clock

Subsidiary dials:
– Seconds at 9 o’clock
– 60-minute counter at 3 o’clock
– Date at 6 o’clock

Corrector push pieces
– Day of week between 8 and 9 o’clock
– Month between 12 and 1 o’clock
– Moon phase between 10 and 11 o’clock
– Date at 12 o’clock

Delivered with correction stylus in ebony with 18K white-gold inlays

950 platinum, cambered sapphire-crystal glass, interchangeable solid platinum and display backs
Water-resistant to 30 meters
Case dimensions: Width (9 to 3 o’clock): 37 mm
Length (6 to 12 o’clock): 37 mm
Length (12 to 6 o’clock, between lugs): 45 mm
Height: 12.35 mm
Width between lugs: 21 mm

Transfer-printed railway track minute scale along entire periphery
12 applied baton-style hour markers in 18K white gold
Leaf-shaped hour and minute hands in 18K white gold
Arrow-style counterbalanced sweep chronograph and rattrapante hands, painted red
Subdials rhodiumed, with circular guilloché patterns:
– Seconds subdial at 9 o’clock: leaf-shaped seconds hand in 18K white gold, painted black
– 60-minute counter at 3 o’clock: leaf-shaped minute-counter hand in 18K white gold, painted red
Date at 6 o’clock on two-tone dial, rhodiumed on the outside ring and black in the center: leaf-shaped hand in 18K white gold, painted white

Hand-stitched alligator with large rectangular scales, matt black with red stitching, platinum prong buckle

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