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.
Movement
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
Indications:
Hours and minutes
Subsidiary seconds at 6 o'clock
10-day power-reserve indication at 12 o'clock
Functions:
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
Features
Case:
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
Dial:
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
