In October 1994, A. Lange & Söhne presented the first collection of the new era, including the legendary TOURBILLON “Pour le Mérite”, the first wristwatch with a tourbillon and a fusée-and-chain transmission. It was followed in 2005 with a further model in which these two elaborate constructions were united: the TOURBOGRAPH “Pour le Mérite”. But there was more: a chronograph with the rattrapante function made it the manufactory’s most complicated watch at the time.

Now, the movement has been endowed with a fifth complication. In the development phase, the integration of a perpetual calendar in the TOURBOGRAPH PERPETUAL “Pour le Mé- rite” presented the engineers of the Saxon manufactory with a formidable challenge: to orchestrate the interaction of the complex mechanisms in such a way that mechanical con- flicts or unwanted energy losses could be prevented. In this project, the perpetual calendar mechanism had to be built around the tourbillon. Consequently, only about two thirds of the movement surface were available, and this necessitated a redesign of the basic calibre. At the same time, the developers did not want to noticeably increase the height of the movement.

A classic concept

The TOURBOGRAPH PERPETUAL “Pour le Mérite” is the epitome of classic watchmaking: its hallmarks permeate all domains from design and engineering to consummate, flawless ar- tisanship. The dial itself reflects the traditional approach in timekeeping. Arabic numerals, a railway-track minute scale, blued steel hands for the time and rhodiumed gold hands for the calendar as well as the cloverleaf arrangement of the subsidiary dials pay tribute to the famous A. Lange & Söhne pocket watches. Tradition also governs technical details such as column-wheel control for the chronograph and rattrapante mechanisms as well as the screw balance. Finally, it manifests itself in typical quality elements such as the two dia- mond endstones that suspend the tourbillon cage or the black-polished tourbillon bridge. The stately platinum case with a diameter of 43 millimetres is a fitting stage for this horo- logical masterpiece.

Perpetual calendar

Of the 684 parts of the new L133.1 manufacture calibre, no fewer than 206 constitute the perpetual calendar with its analogue displays. It will correctly indicate the duration of each month until 2100. A one-time correction will be needed on the last day of February in this secular year. From then on, the calendar will again be correctly calibrated for the next hun- dred years. It has three subsidiary dials. The date at 12 o’clock and the day at 9 o’clock are indicated with rhodiumed gold hands. The month and leap year are both displayed at 3 o’clock. The upper half of the analogue date also accommodates the moon-phase display which is calculated to remain accurate for 122.6 years. Its deep-blue disc is made of solid gold. During the development of the calendar module to be built around the tourbillon, great emphasis was placed on space-saving architecture.

Chronograph with rattrapante function

The development of highly complex chronographs and their meaningful interaction with other functions is among the Saxon manufactory’s key skills. Apart from the two chrono- graph pushers on both sides of the crown, a third button at 10 o’clock modestly reveals that the TOURBOGRAPH PERPETUAL “Pour le Mérite” deserves a place in the top-tier category of split-seconds chronographs. The fascinating function of the split-seconds mechanism can be observed in great detail with a look through the sapphire-crystal caseback. The precise control of the gold-plated chronograph hand and the blued rattrapante hand is handled by two column wheels. During a complete revolution of the 30-minute counter at 9 o’clock, as many lap times as needed can be stopped.

The combination of a perpetual calendar with a split-seconds chronograph is very rare. Power management is an especially challenging undertaking. In particular, the simultane- ous use of several functions calls for mechanical ingenuity, for instance when the calendar indications advance around midnight and the stopwatch function is used at the same time. Assembling such a movement requires considerable experience and exceptional sensitiv- ity when adjusting and harmonising the mechanisms.

One-minute tourbillon

In the way they flawlessly interact, the tourbillon and the fusée-and-chain transmission offset two disruptive phenomena in a mechanical movement: gravity and waning spring force. Thus, they contribute to improved rate stability and rate accuracy. The L133.1 move- ment that works inside the TOURBOGRAPH PERPETUAL “Pour le Mérite” is already the tenth calibre with the delicately linked mechanism that overcomes the pull of gravity. The tradi- tional black polish of the tourbillon bridge integrated in the dial imposes new challenges on the finisseurs because for the first time ever, this complex finishing technique is being applied to a curved surface.

Fusée-and-chain transmission

The results of A. Lange & Söhne’s efforts to develop intelligent energy management sys- tems for mechanical movements – and thus to compensate for the unavoidable torque loss of the mainspring barrel – include three different constant-force escapements as well as the fusée-and-chain transmission which was integrated in a wristwatch for the first time in 1994. It is the technical hallmark shared by all timepieces identified by the attribute “Pour le Mérite” in reference to the erstwhile Prussian order conferred for exceptional sci- entific merit. Via a fusée connected to the spring barrel with a chain, the force of the main- spring is delivered to the movement in constant increments thanks to the ingenious way in which the principle of levers is harnessed. A planetary gearing mechanism inside the fusée ssures that the flow of power from the mainspring barrel to the escapement is not inter- rupted while the watch is being wound. The filigreed yet robust mechanism requires the utmost in attention as regards design, production, finissage, and assembly.

Perfection down to the last detail

The TOURBOGRAPH PERPETUAL “Pour le Mérite” is being crafted in a limited edition of only 50 platinum-cased watches. The finish of the manufacture calibre complies with the high- est standards of Saxon watchmaking artistry. Thermally blued screws, screwed gold cha- tons, bridges and plates made of untreated German silver and decorated with Glashütte ribbing and perlage as well as the hand-engraved chronograph bridge round out the high- lights of the classic complication.