Patek Philippe's '10 Day Tourbillon'

April 2003

With its '10 Day Tourbillon', Patek Philippe wants to reassert 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.

Totally new tourbillon

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.

The strictest of controls

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 'régleurs' 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.

10-day power reserve

Patek Philippe presented three years ago the 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.

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. Although understatement is a hallmark of Patek Philippe, the 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 the beautiful and intricately crafted tourbillon cage is visible through the sapphire crystal caseback.

An exquisite statement

The accented rectangular shape of the platinum case in the art déco style is reminiscent of the great classics of the 1920s and 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 millimetres. 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 'vintage rose' 18 carat 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 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.