acheron Constantin celebrates its 270th anniversary and its quest for excellence with a new series of Les Cabinotiers watches entitled ‘La Quête’, which pays tribute to astronomy and the odysseys of ancient times. Representing significant technical and aesthetic challenges, these pieces highlight Vacheron Constantin’s expertise in creating grand complication watches enhanced by artistic crafts.

The Cosmica Duo – Grand Complication, a single-piece edition, showcases two worlds thanks to an ingenious reversibility system: one dial transports observers to the stars, while the other immerses them in the kinetic artistry of the new Calibre 2756-B1. Astronomical functions are the main focus of this grand complication watch, which also incorporates a minute repeater and a tourbillon.

The observation of the stars, the cycle of the seasons and the alternation of day and night have always aroused human curiosity, and from very early times, mankind sought to model these phenomena. Thanks to the first astronomical observatories, space-time became a more concrete concept, explained in terms of measurable cycles.

The double-sided watch features 24 complications, mainly astronomical and including a minute repeater and a tourbillon regulator, orchestrated by the new Calibre 2756-B1. This movement, which took four years to develop, is issued from the base of the Calibre 2756 presented in 2020. The base movement that powers the minute repeater and tourbillon has undergone a few modifications, while the two additional plates have been almost entirely redeveloped. One controls the perpetual calendar and celestial chart; the other is used for astronomical indications.

One dial, in predominantly blue tones, offers a sidereal journey, in addition to the essential time and calendar references. The symmetry of the dial, which ensures clear legibility of the indications, belies the complexity of its construction, which comprises 22 parts. The off- centre hour and minute counter also displays a Northern Hemisphere sky chart. As it rotates, it reproduces the movement of the constellations according to the length of a sidereal day, which is marked on the periphery. Taking a fixed star in the sky as a reference point, the time it takes for the Earth to complete a full 360° rotation, or sidereal day, is exactly 23 hours, 56 minutes and 4 seconds. As the Earth rotates on its axis at the same time as it revolves around the sun, it takes approximately four minutes less than a calendar day to return to its original point in relation to the given star. A light-coloured ellipse highlights what the observer can see in real time.

This dial configuration frees up space for the two perpetual calendar counters. One at 5 o’clock uses hands to indicate the months and the leap years on an 8-year cycle. The other, at 7 o’clock, displays the days and dates, also with hands. The central time functions are complemented by a second time zone indicated by a coaxial hand, open-worked and coloured orange. Local time and home time each have a day/night counter, at 4 o’clock and 8 o’clock respectively, while a window at 6 o’clock displays the name of the city chosen from among the 24 time zones, for the indication of the second time zone.

In contrast to the celestial poetry of that dial, the other – an open-face dial constructed from 28 parts – reveals the mechanical heart of the calibre. The central hands, including the minute hand bearing the symbol of the sun, indicate true solar time. Based on the apparent movement of the Sun, this varies from civil time due to the inclination of Earth’s axis and its elliptical orbit. Mean solar time, or civil time, which governs our daily lives, coincides with true solar time only four times a year at the solstices and equinoxes. The differences, ranging from -16 minutes and 23 seconds to +14 minutes and 22 seconds per day, constitute the equation of time. Calibre 2756-B1presents this as a running equation of time, enabling the solar and civil times to be read simultaneously, one on each side of the watch. The indications of sunrise and sunset times and the length of day and night, positioned at 3 o’clock and 9 o’clock, complete this ‘solar’ information. At 6 o’clock, the age and phases of the moon are displayed by a retrograde hand on a semi-circular counter. The precision moon phase requires only one correction every 1,000 years.

In addition to its technical complexity and distinctive design, the originality of this piece lies in its reversibility. Measuring 47 mm in diameter and 20.20 mm in height, a feat in itself given the complexity of a movement comprising 1,003 components, the white gold case features articulated lugs with removable strap attachments that can be secured on either side of the fixing bars without the need for tools. The challenge in designing such a system lies in its ergonomics, ensuring that the watch is comfortable to wear regardless of which side is chosen. The lugs are therefore short with a rounded profile, holding the watch in place without needing to rest on the wrist, and enabling the alligator leather strap to be freely reversed. This ensures that, as well as remaining stable, the watch is also comfortable, as only the strap is in contact with the wrist. Depending on the wearer’s preferred time measurement, the Cosmica Duo – Grand Complication watch displays either mean civil time or true solar time with the ability to switch from one to the other in an instant by turning the watch over.

The case design has been carefully considered to simplify the control of the functions. A push- button integrated into the crown sets the second time zone, while a selector located in the case side can lock the sky chart in place when setting the watch. The minute repeater lever has been specially designed and positioned in the centre of the case side to maintain the symmetry of the watch regardless of which side the wearer prefers.

A highly complex astronomical timepiece, the Cosmica Duo – Grand Complication is also a musical watch with a minute repeater. To create this on-demand striking mechanism, which – given its melodic dimension – is one of the most delicate of all horological complications, the engineers and master watchmakers at Vacheron Constantin drew inspiration from the work carried out on the 2005 La Tour de l’Île watch. Of particular note is the striking regulator, introduced in that watch, which governs the striking of the gongs by the hammers. This system, visible through the open-worked dial at 8 o’clock, perfectly regulates the duration of the musical sequences played for the hours, quarters and minutes. Operating in complete silence, it ensures distinct, harmonious and perfectly rhythmical chimes. The system is distinguished by its two weights with a remarkable shape optimised to generate a kind of ‘engine brake’ through centripetal force acting on the striking bar, thus smoothing out the energy released by the barrel.

Operating at 18,000 vibrations per hour (2.5 Hz), the escapement regulator is integrated into a tourbillon positioned at 12 o’clock. By constantly changing the position of the regulator to counteract the effects of Earth’s gravity on the amplitude of the balance wheel, the tourbillon is synonymous with increased movement precision. The tourbillon cage takes the form of a Maltese cross, the emblem of Vacheron Constantin and the mechanism is topped by the retrograde power reserve indicator, an additional challenge in terms of construction.

All the elements of the dial are finely finished: the mother-of-pearl inserts on the sidereal hour circle are tinted blue; the opaline dial has a circular-satin-finished outer edge, while the perpetual calendar counters are circular-satin-finished with azuré centres; the white gold hour markers are lacquered and the edge of the sky chart is fluted.

The reverse side is radically different. Giving strong expression to the complexity of the skeletonised Calibre 2756-B1while ensuring legibility, the power reserve, moon phases and indications of day and night and sunrise and sunset are marked on discreet inserts of blue-tinted mother-of-pearl. The inserts are constructed on two levels, strengthening the three-dimensional effect. To accentuate the airy feel of the retrograde moon phase display and the depth of the movement, five domed moons in 18K gold are mounted on an arc of sapphire crystal at the bottom of the dial. The periphery of the dial is opaline with circular satin finishing.

This open-worked dial reveals the beauty of the movement finishes, which is enhanced by the champagne colour of the components, created by galvanic treatment. Circling decorates the plates and the hand-bevelled bridges are decorated with Côtes de Genève and circling. The rockers are sunburst-brushed, while the wheels are circled and the gears are mirror- polished. The alternation of sandblasted and circular grained surfaces further accentuates the technical nature of this piece.

TECHNICAL SPECIFICATIONS

• REFERENCE 9780C/000G-087C Timepiece certified by the Hallmark of Geneva

• CALIBER 2756-B1 Developed and manufactured by Vacheron Constantin Mechanical with manual winding 33.30 mm diameter, 12.45 mm thickness Movement power reserve: approximately 60 hours 2.5 Hz (18,000 vibrations/hour) 1,003 components 112 jewels 24 complications

• INDICATIONS Off-centred hours and minutes, day/night indicator, second time zone, 24-city indicator, day/night indicator for the second time zone, perpetual calendar, sky chart of the Northern Hemisphere with local horizon zone indication, sidereal hours and minutes, minute repeater, running equation of time (hours and minutes), sunrise and sunset times, day and night duration, retrograde precision moon phase and age, tourbillon, power reserve indicator

• CASE 18K white gold, reversible 47 mm diameter, 20.20 mm thick Double-sided

• DIAL Side 1: Blue opaline with circular satin-finished outer edge; blue mother-of-pearl inserts; opaline, circular satin-finished and azuré counters; lacquered 18K white gold applied hour markers Side 2: Open-worked with blue circular satin-finished and opaline outer edge; blue mother-of-pearl counters; 750/1000 3N yellow gold moons; lacquered 18K white gold applied hour markers 18K gold hands

• STRAP Dark blue Mississippiensis alligator leather with alligator leather lining, hand-stitched, saddle-stitched finish, large square scales

• CLASP 18K white gold folding clasp

• CASE&ACCESSORY Les Cabinotiers model Includes a corrector ‘pen’