A. Lange & Söhne: 1815 Rattrapante Perpetual Calendar

With its launch in 2013, the 1815 Rattrapante Perpetual Calendar marked a milestone in A. Lange & Söhne’s more recent history: no less than seven chronograph calibres had previously been crafted by the Saxon manufactory. Equipped with a specially developed movement, it united three of the most elaborate complications while maintaining the classic, elegant design of the 1815 watch family. Today the Brand presents it again in a new limited edition of 100 pieces with a white gold case and a pink gold dial.

ACCURACY OF ONE SIXTH OF A SECOND

The rattrapante function of the Rattrapante Perpetual Calendar represents one of the greatest horological challenges. In addition to the conventional functions of a chronograph, this complication is capable of measuring intermediate times and comparative times as well as determining minimum and maximum values in the course of one minute. Since the balance wheel of the manufacture calibre L101.1 beats with six semi-oscillations per second, the stopped times can be recorded with an accuracy of one sixth of a second. High-precision readings are assured thanks to the additional graduation on the peripheral minute scale. 

The precisely orchestrated proceedings within the movement can be observed through the sapphire-crystal caseback. The classic two-column wheel transmission is used to control the measurement of stopped and intermediate times. As is typical for A. Lange & Söhne, technical intricacy is coupled with a high degree of artisanship. The upper surfaces of all moving parts are decorated with straight graining while the peripheral chamfers are polished. 

THE PERPETUAL CALENDAR

While the rattrapante chronograph is capable of measuring different time intervals to a fraction of a second, the technical feat of the perpetual calendar lies in its “long-term memory”. As its name suggests, the complex and prescient mechanism ensures that the date, day of the week and month are correctly displayed ‒ every single day, during decades, even taking leap years into account. The calendar indications must only be corrected by one day but not until 1 March 2100; according to the rules of the Gregorian calendar, the leap year will then be skipped. 

The high-precision moon-phase display has also been programmed with the long term in mind. It so closely emulates the duration of the synodic orbit of the earth’s satellite that it would take 122.6 years for the display to be corrected by one day. 

THE DESIGN

Not only the technical details distinguish the 1815 Rattrapante Perpetual Calendar but also the well-organised arrangement of its displays. Following the Datograph Perpetual Tourbillon (2019) and the LANGE 1 Perpetual calendar (2021), it is the third A. Lange & Söhne timepiece showcasing an 18-carat pink gold dial: the warm, golden hue contrasts elegantly with the cool white gold of the case. With a traditional railway-track minute scale, Arabic numerals and the harmonious arrangement of the four subsidiary dials, the dial embodies the essence of the watch family named after the birth year of Ferdinand Adolph Lange. 

The manifold displays of the perpetual calendar and the rattrapante chronograph echo the classic aesthetics of earlier Lange pocket watches. The two pairs of combined calendar indications are arranged at 3 and 9 o’clock. The left subsidiary dial shows the date and day of the week, the right the month and leap year. Sharing an auxiliary dial with the subsidiary seconds at 6 o’clock, the moon-phase display provides an expressive colourful accent. The minute counter and power-reserve indicator are located at 12 o’clock. The shorter gold hand in the inner circle reveals when it is time to deliver new power to the movement via the winding crown. The longer hand made of blued steel imparts information about the stopped minutes. 

THE IN-HOUSE CALIBRE L101.1

Incorporating traditional design and engineering features, the manually wound movement L101.1 totals an impressive number of 631 individual parts. The mechanism of the perpetual calendar alone requires 211 components, a further 206 account for the rattrapante-chronograph mechanism. A screw balance, which is driven by the balance spring developed and manufactured in-house, ensures high rate stability. Lange-typical quality hallmarks such as screwed gold chatons, blued screws, an elaborate whiplash precision index adjuster and the hand-engraved balance cock are visible through the sapphire-crystal caseback. The finissage of the movement, which is assembled twice, reflects A. Lange & Söhne’s high standards in every single detail. 

“With three classic complications, the manufacture calibre L101.1 is one of our most complex movements. Each one in itself already constitutes a technical feat; when combined, they represent a far greater challenge. For our designers and our watchmakers in equal measure, since the tweaking and tuning process of all mechanisms requires an exceptionally high degree of dexterity and technical expertise,” explains Anthony de Haas, Director of Product Development at A. Lange & Söhne. 

THREE VERSIONS

The dimensions of the new 1815 RATTRAPANTE PERPETUAL CALENDAR remain unchanged: the case boasts a diameter of 41.9 millimetres and a height of 14.7 millimetres. In addition to the new 1815 RATTRAPANTE PERPETUAL CALENDAR in white gold with a pink-gold dial limited to 100 pieces, the model also comes in a platinum/argenté and pink-gold/argenté case/dial combination. (Price on request)