Vacheron Constantin’s Les Cabinotiers Dual Moon Grand Complication is an extremely complex one-of-a-kind double-sided watch. Powered by the new manual-winding in-house Calibre 2755 TMRCCQP, it features eleven horological complications including a minute repeater, a perpetual calendar, precision moon phases and a sky chart.
On the front of the watch, the eye is drawn to the central depiction of the moons in the two hemispheres. The moons rotate on a blue titanium disc shaped like a starry dome which is coaxial with the central hands. The age of the Moon is indicated around a periphery scale graduated from 1 to 29½. The blue-sky background was obtained by physical vapour deposition (PVD), while the uneven surface of the moon, like the tiny stars, was achieved by diamond cutting.
The display of the hours and minutes has been slightly off-centred upwards to integrate the calendar indications. Instead of the traditional pointer-type dials, this watch has rotating discs. This solution, which does not need any correction before 2100, is more complex on a technical level but offers more convenient readings. The semi-instantaneous display of the day and the instantaneous display of the month and leap year appear through apertures, as does the date display.
The four-part dial construction comprises a 0.35 mm thick sapphire dome placed on a silver-toned metal baseplate with a sandblasted finish. The dome beneath which the moon-phase disc turns is fitted with two ‘masks’ whose smoky appearance is achieved by metallisation. It is held in place by a curved brass ring, satin-brushed with an opaline varnish, which in turn bears the white gold hour-markers.
The architecture of the dial on the reverse side displays a sidereal time and constellations against a celestial backdrop, along with the tourbillon regulator. Using a fixed star in the sky as a reference point, the time it takes the Earth to complete a full 360° revolution – or sidereal day – is exactly 23 hours, 56 minutes and 4 seconds. As the Earth both spins on its axis and revolves around the sun, it takes about four minutes to return to its starting point in relation to the given star.
A fixed dial, bearing a blue dot representing the celestial horizon, is positioned below a movable sapphire crystal engraved with the constellations, while the rim features month markings as well as five-day graduations. By performing a complete rotation according to sidereal time, this mobile disc gives the exact position of the constellations – delimited by the celestial horizon – at the time when the watch is consulted by pointing it Northwards. Sideral time is read off counter-clockwise, facing the current date on the fixed PVD-treated blue outer ring bearing a 24-hour scale along with the cardinal points.
The one-minute-rotating tourbillon is distinguished by its carriage shaped like Vacheron Constantin’s Maltese cross emblem, with its delicately hand-polished bar. To diminish the weight (hence improving performance) as well as for aesthetic reasons, the tourbillon components have been skeletonised – notably the fixed wheel which is entirely open-worked.
The watch’s particularly complex minute repeater striking mechanism, controlled by a repeater slide housed on the caseband, drew inspiration from La Tour de l’Île. This double-sided anniversary watch produced in a seven-piece edition for the Maison’s 250th anniversary is the most complicated wristwatch ever made with its 16 complications, including a minute repeater with a centripetal strike regulator.
This silent system also found in the Dual Moon Grand Complication enables the duration of the musical sequences to be perfectly timed in order to obtain a distinct and harmonious sound of the notes played for the hours, quarters and minutes by the hammers striking two circular gongs. As an additional feature, the gongs of this repeater have been slightly ovalised to avoid them overlapping the tourbillon and without affecting their crystal-clear sound.
The watch’s in-house Calibre 2755 TMRCCQP, one of VC’s major developments, was chosen to orchestrate its eleven functions. Beating at a rate of 18,000 vibrations per hour, its 774 components are the embodiment of elegance amid complexity. It has a 58-hour power reserve. The movement has been meticulously finished with circular satin-brushed and hand-bevelled, with a Côtes de Genève motif on the rear bridges as well as mirror-polished hammers and strike-regulator bar.
To ensure a smoother match with the 46 mm-diameter case in 18K white gold, it has also been entirely rhodium-plated. As is the case with all timepieces from the Maison, this model showcases the extreme attention to detail lavished on every component, even those that remain invisible once the movement has been assembled.
The Dual Moon Grand Complication, the latest mechanical masterpiece from Vacheron Constantin’s fabled Les Cabinotiers department, is just as pleasing to the eyes as it is boggling to the mind. It puts on a spectacular astronomical show that’s easy to decipher, while masking the immense innovation and complexity behind it. And as with all Les Cabinotiers creations, this one-of-a-kind timepiece is a marvel to behold.
