The Ref. 5101P “10 DAY TOURBILLON”: Patek Philippe’s latest masterpiece

This latest masterpiece from the workshops in Geneva is the first watch that combines two complications which are very difficult to accommodate in such a small space: two mainspring barrels connected in tandem for 10 days' power reserve and a tourbillon which rotates about its own axis once a minute and can be viewed through the sapphire crystal caseback.

As all Patek Philippe tourbillon wristwatches, the rectangular movement of the 5101P is a chronometer officially certified by the C.O.S.C.; it also displays the Geneva Seal.

Platinum case (950) in the art déco style, water-resistant to 25 meters.

What is left for a manufacture to do after it has broken almost all records in the domain of horological complications? Patek Philippe built the most complicated portable mechanical watch ever made (The Calibre 89), devised the world’s most ingenious ensemble of complications (the Star Caliber 2000), and crafted the most fascinating Grande Complication wristwatch with astronomical indications (the Sky Moon Tourbillon). The answer is simple: It reasserts its leadership by combining challenging complications in a way that has never been attempted before. The result is the Ref. 5101P wrist chronometer with a power reserve of 10 days and a tourbillon.

It takes much more than just a cursory glance at Patek Philippe’s debut showpiece for Basel 2003 to realize that this is a highly complicated wristwatch. A closer look reveals a few cues that point to the remarkable personality of this watch: The dial has a 10-day power-reserve scale, displays the discreet inscription “Tourbillon”, and bears the individual serial number of the movement. Once again, Patek Philippe transcended boundaries with the Ref. 5101P “10 DAY TOURBILLON” by fitting two mainspring barrels plus a tourbillon in the compact space of a rectangular form movement.

The basic caliber 28-20/220 with an energy storage capacity of 240 hours already existed – in the year 2000, it was presented in a limited edition for the Ref. 5100 “10 DAYS” wrist chronometer. For this reason, the development and construction of the new caliber 28-20/222 movement required “only” three years. The greatest amount of time was invested in the creation of a totally new tourbillon. To prevent the minute wheel or third wheel from obstructing the view of the tourbillon, the entire going train was relocated to the dial side. The tourbillon is now showcased on the bridge side as the dominant element. A look through the sapphire-crystal caseback affords a splendid view of the circular-grained plate and the bridges with Geneva striping, six jewels secured in gold chatons, the mirror-polished tourbillon bridge, and the tourbillon cage which embraces the Gyromax balance wheel, one of the pioneering inventions to Patek Philippe's credit. As all mechanical calibers crafted by Patek Philippe, this movement also displays the Geneva Seal, recognized as the most prestigious official hallmark of impeccable craftsmanship.

The tourbillon – an ingenious twist for enhanced accuracy 

To this very day, the tourbillon – French for whirlwind – is considered to be one of the most fascinating complications ever devised. It pays tribute to the unfaltering quest among watchmakers to continually improve the precision of their masterpieces. The function of the tourbillon makes a case in point. It was in the 18th century when inquisitive minds discovered that the spring of the balance – the beating "heart" that regulates portable watches – has a systemic error. Because of its helical shape, the spring’s center of gravity is not precisely in the middle. The consequence is that the regularity of its oscillations is affected by the earth's pull as soon as the watch is moved out of the horizontal position. The tourbillon corrects this interference because it suspends the balance wheel and balance spring in a cage that rotates about its own axis once a minute. Thus, the position error is automatically offset.

Rarely has this problem been solved with such acumen as with the tourbillon designs for the legendary Patek Philippe wrist chronometer movement No. 861 115 and in the tonneau-shaped Patek Philippe 34T wrist chronometer caliber which together dominated the precision competitions of the Geneva observatory in the 1950s and 1960s. The cages in these extraordinary movements inspired the design of the tourbillon of the Ref. 5101P. The Patek Philippe open-face chronometer with tourbillon caliber No. 198 411 deserves mention here as well: In 1962, it set the world precision record for mechanical watches at the observatory in Geneva. It remains unbroken to date.

The effort involved in attaining such benchmark levels of precision is aptly reflected in the tourbillon of the new Ref. 5101P “10 DAY TOURBILLON” model.

Although the rotating cage alone is composed of 72 individual parts, it weighs only a scant 0.3 grams. This suggests how tiny the components must be. It takes a highly specialized watchmaker an entire week just to craft the cage. Several hundred steps as well as a steady hand and a trained eye are required to bevel the edges, satin-finish the flanks, apply chamfers, and polish the surfaces. Even the production of the seemingly simple, mirror-polished tourbillon bridge commands the attention of an experienced watchmaker for two whole days. And this by far does not exhaust the list of timeconsuming operations.

As all Patek Philippe tourbillon wristwatches, each Ref. 5101P is delivered with an official watch rate certificate of the C.O.S.C. (Contrôle Officiel Suisse de Chronomètres). Since the main purpose of the tourbillon is to improve the rate accuracy of the watch, Patek Philippe imposes very strict standards on its tourbillon timepieces. Specially trained regleurs spend at least a full week precision-adjusting these watches. Subsequently, during a 15-day period, the movements are thoroughly tested by the C.O.S.C. After having passed the C.O.S.C. tests, each chronometer is submitted to company president Philippe Stern. He personally makes the decision whether the chronometer merits the “Patek Philippe Tourbillon” designation or needs to undergo the entire procedure again. Because the in-house requirements imposed on chronometers by Patek Philippe are twice as strict as those of the official testing institute, a tourbillon wristwatch may have to be precision-adjusted a second time and then sent back to the C.O.S.C. for renewed testing. The Ref. 5101P is delivered with an exclusive certificate issued jointly by the Official Swiss Chronometer Bureau and the Geneva Seal Institute.

A wristwatch with 10 days’ power reserve: unprecedented 

People who cherish mechanical watches appreciate the convenience of not having to readjust the hands each time they set their watch aside for a few days. Patek Philippe accommodated them three years ago with the unique Ref. 5100 “10 DAYS” – the world’s first wristwatch with a power reserve of 10 days. This record-breaking energy reserve stands unchallenged to date, and for the first time is now also available in a tourbillon wristwatch.

To store this much winding energy, the caliber 28-20/222 movement features twin mainspring barrels matched in size to maximize their storage capacity. The two barrels are wound simultaneously and act similar to so-called communicating vessels. A coupling system with a slipping bridle spring on the first barrel prevents the mainsprings from being wound past their limit by disengaging the barrels as soon as they are fully wound. On the dial, the power-reserve indication at 12 o'clock informs the owner how long the movement will keep running before it has to be rewound.

When determining the transmission ratios in the winding train, Patek Philippe’s engineers took into consideration that the effort required to fully wind the watch (about 100 revolutions of the crown) should correlate reasonably with the 10-day power reserve. Thus, half a turn of the crown is already sufficient to build up a power reserve of slightly more than one hour. In conventional watches, it takes one full revolution to do this.

A power reserve of 10 days is a milestone in the history of watchmaking. The technology behind this achievement and the aesthetic fashion in which it was incorporated into a captivating timepiece reflect the finest traditions of Patek Philippe, upheld for more than 160 years without interruption. The company’s heritage has always been inspired by an innovative spirit and the determination to focus on utility. Patek Philippe will spare no effort to further expand its undisputed lead in horological complications and continuously explore ways to keep its products on par with changing lifestyles in an evolving world.

The rationale of discretion 

Typically enough for Patek Philippe, hardly anything on the outside of the Ref. 5101P suggests the complexity of its inner workings. Apart from the 10-day power-reserve indication, the dial merely has two subtle pointers of pedigree: The word “Tourbillon” and the serial number of the movement in delicate script. Although understatement is a hallmark of Patek Philippe, the fascinating complications of the Ref. 5101P are concealed at first sight for a very pragmatic reason. The oil needed to lubricate the tourbillon can decompose when exposed to ultraviolet radiation and therefore, it could lose its beneficial tribological properties within a matter of months. The consequences would be friction, wear, and a degradation of the rate accuracy of the watch. This is certainly not a tolerable fate for a timepiece designed for superior precision. Hence, Patek Philippe prefers not to expose tourbillons to direct sunlight through an aperture in the dial. But fortunately, the beautiful and intricately crafted tourbillon cage is visible through the sapphire-crystal caseback and its steady, minute-by-minute rotation is indeed a mesmerizing sight to behold.

An exquisite statement

An inimitable movement like the caliber 28-20/222 deserves a case that does justice to its ingenuity. The accented rectangular shape of the platinum case in the art déco style is reminiscent of the great classics of the 1930s. It owes its subtle elegance to the sleek, three-tiered flanks and the anatomically curved silhouette which makes it gently hug the wrist – even though it is longer than fifty millimeters. The camber of the case is followed by the convex glass, ground in parallel planes inside and outside to prevent optical distortion. It protects the satiny sheen of the attractive “vintage rose” 18K gold dial with its subsidiary seconds display at 6 o'clock and the 10-day power-reserve scale at 12 o'clock. The hours and minutes are indicated by feuille hands made of black-oxidized gold and applied Breguet-style gold numerals that are also blackened. The sapphire-crystal caseback reveals the meticulously decorated plate with jewels set in gold chatons and the intricate tourbillon. A discreet diamond positioned between the lugs at 6 o'clock indicates that the case of the Ref. 5101P is made of solid platinum. The watch is worn with a hand-stitched brown crocodile strap that is secured with a platinum prong buckle to match the case.

Because of the immense amount of work needed to craft it, the Ref. 5101P “10 DAY TOURBILLON” will always remain a rare timepiece. Only a few dozen of these watches are likely to be manufactured each year.

Technical data

Patek Philippe Ref. 5101P “10 DAY TOURBILLON”:
Rectangular chronometer with manually wound caliber 28-20/222, tourbillon, 10 days’ power reserve, power-reserve indication, and subsidiary seconds.


Dimensions: 28 x 20 mm
Overall height: 6.30 mm
Number of parts: 231, of which 72 for the tourbillon
Number of jewels: 29, of which 6 are set in gold chatons
Power reserve: 10 days (240 hours) with two mainspring barrels connected in tandem
Balance: Gyromax
Frequency: 21,600 semi-oscillations per hour
Balance spring: Breguet
Tourbillon rate: One revolution per minute
Manual winding: About 100 turns of the crown until fully wound

Hours and minutes
Subsidiary seconds at 6 o'clock
10-day power-reserve indication at 12 o'clock

Winding crown with two positions:
Pulled out to set the time
Pushed in to wind the movement

Certification: Exclusive certificate issued jointly by the Official Swiss Chronometer Bureau and the Geneva Seal Institute

Hallmarks: Geneva Seal


Platinum case (950) with convex sapphire-crystal glass and sapphire-crystal caseback, Top Wesselton diamond between the lugs at 6 o’clock.
Water-resistant to 25 meters

Case dimensions: L x W x H: 51.70 x 29.60 x 12.20 mm

18K yellow gold with “vintage rose” hue
Applied Breguet numerals and hour markers in black-oxidized 18K gold
Feuille minute and hour hands in black-oxidized 18K gold
Power-reserve indicator hand in black-oxidized 18K gold
Baton seconds hand in black-oxidized 18K gold

Strap: Brown hand-stitched crocodile strap with platinum prong buckle

Ref. 5101 – 10-day power reserve, tourbillon

Movement finishing and decoration – Dial side of the movement
The countersinks of screw bores are polished. The screw heads and slots are angled and polished.
The engravings on the plate and bridges as well as the Geneva Seal are gold-plated.
The angling of the movement bridges, executed by a master watchmaker, is deliberately more pronounced than traditional angling, which gives the manually wound mechanical caliber of the «10 Day Tourbillon» inimitable aesthetic appeal.
Six of the 29 jewels are set in 18K gold chatons.
The bridges are angled and polished, and their flanks are burnished. The upper sides are decorated with Geneva striping. The undersides are delicately circular-grained.
The ends of the staffs and arbors are rounded and polished.
The steel bridge of the tourbillon is angled and mirror-polished by hand. The crossbar is rounded and polished by hand; its flanks are burnished by hand.
All of the steel parts of the tourbillon cage are angled and mirror-polished by hand; the flanks are burnished by hand.
The six re-entrant angles are finished by hand, an operation which requires the utmost in precision and the steady hand of a highly experienced watchmaker.
Geneva Seal.
The tourbillon cage is manually balanced by the watchmaker who assembles it.
Movement finishing and decoration – Case back side of the movement
As stipulated by the Geneva Seal criteria, all steel parts (leaf springs, yokes, levers) are angled and polished; their flanks and upper sides are burnished by hand.
The countersinks of screw bores are polished. The screw heads and slots are angled and polished.
The angling of the movement bridges, executed by a master watchmaker, is deliberately more pronounced than traditional angling, which gives the manually wound mechanical caliber of the «10 Day Tourbillon» inimitable aesthetic appeal.
The plate features fine circular graining.
Every tooth of each wheel and pinion in steel is polished individually with a rotating hardwood disc.
The brass wheels are gold-plated and their spokes are angled.
The ends of the staffs and arbors are rounded and polished.
The bridges are angled and polished; their flanks are burnished. The upper sides are burnished and rubbed, and the undersides are delicately circular-grained.
The countersinks of the jewels are polished.

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