Vacheron Constantin Métiers d'Art The Legend of the Chinese Zodiac Year of the Horse (86073/000P-9832)

For 2010, Vacheron Constantin presents the Patrimony Traditionnelle "Calibre 2253" watch in the Collection Excellence Platine. This model features a major astronomical complication in terms of technical application. Entirely constructed by Vacheron Constantin's engineering department and developed over several thousands of hours, the new Calibre 2253 provides information derived from Earth's orbit around the sun, notably a perpetual calendar, the equation of time and the times of sunrise and sunset. It has a tourbillon escapement as well.
A power reserve of around 336 hours or 14 days
To celebrate its 250th anniversary in 2005, Vacheron Constantin introduced the Saint-Gervais watch. Its Calibre 2250 tourbillon movement with a perpetual calendar had the then exceptional running time of 250 hours from the energy stored in four mainspring barrels. The experience gained in making the Calibre 2250 was applied to the development of the Calibre 2253. The new movement benefited from the latest techniques deployed by the manufacturer's technicians, engineers and watchmakers.
Despite supporting extra mechanical complexity, the Calibre 2253 exhibits a breathtaking amount of power reserve - some 336 hours or 14 days of running time drawn from two pairs of coupled barrels. The power reserve is shown through the sapphire-crystal caseback.

The fascinating equation of time
The equation of time is probably the most fascinating complication in this outstanding model. Its purpose is to indicate the difference in minutes between the variable solar time shown by a sundial and the constant mean time of clocks and watches. For practical reasons, mankind has divided each year into 365 and a quarter days, each day into 24 hours, and the hours into 60 minutes each. However, because the Earth's orbit is elliptical rather than circular, the time in relation to the sun varies daily. The noon zenith of the sun when it crosses the observer's meridian seldom occurs at exactly 12 o'clock by his watch. In fact solar time and mean time coincide just four times a year - on April 15, June 14, September 1 and December 24. For the rest of the year, the difference between solar and mean time varies from minus 16 minutes to plus 16 minutes.
The oldest clock showing the equation of time was made by the mathematician Nikolaus Mercator in the 17th century. It enabled folk to covert the sun's varying noon to the standard constant time shown on their watches. Since then, the rare instruments calculating the equation of time have been the work of extremely accomplished horologists.
Making this complication work does indeed call for particular skill. It depends on the equation cam, a waisted oval, shaped like a figure 8 and calculated according to the daily declination of the sun observed from a given spot. The cam rotates once a year while a hand following its contour indicates the equation of time at between 10 and 11 o'clock on the dial of the Patrimony Traditionnelle "Calibre 2253" timepiece of the Collection Excellence Platine.
When the sun rises and sinks
This timepiece displays another function seldom found in watches - the times of sunrise and sunset throughout the year at a given locality. This tricky complication also relies on a cam, the outline of which is calculated according to the latitude of the locality. It demonstrates both the skill of the manufacture's engineers and watchmakers and Vacheron Constantin's attention to its clients, for they can choose the place of the sunrises and sunsets. To this extent it's a custom-made complication where the dials are paired at 8 o'clock and 4 o'clock on the face.
The tourbillon carriage, as always in the shape of the brand emblem, a Maltese Cross, rotates once a minute at 6 o'clock as a small seconds indication. The indications of the perpetual calendar are symmetrically laid out with the days, the months and the dates at 9, 12 and 3 o'clock respectively. The leap-year indicator makes a circumspect appearance on the upper right.  

An exceptional level of finish
The sophisticated finish of this watch is taken to the limits to match its complexity. As part of the Collection Excellence Platine this Patrimony Traditionnelle "Calibre 2253" unsurprisingly incorporates many elements in platinum, from its 43 mm case, water-resistant at a pressure of 3 bar or 30 meters, to its dial hallmarked "PT950", its crown and its folding clasp in the shape of a halved Maltese Cross. There is one other most unusual, if not unique, horological feature: even the Dauphine hands that show the hours and minutes are fashioned in the same material - an incredible technical prowess. The decoration of the dial alternates silvered and frosted surfaces, with snailed chapters, circular-brushed subdials and diamond-polished filets. The applied hour markers and Maltese Cross are in white gold.
The Calibre 2253 movement also bears the prestigious Hallmark of Geneva, which is an independent and legally sanctioned label of workmanship, origin, precision, resilience and competence. This seal of watchmaking perfection, among the oldest of professional labels, is reserved for a handful of Geneva manufacturers. It means that such decorative aspects of the movement as Côtes de Geneve, circular graining, chamfering and straight graining of the steelwork are entirely done by hand.
The finish of the thin bridge that holds the tourbillon is an example among many. It consists of rounding off the top of the rectangular steel bar with a file to create a gleaming barrel-vault along its upper length. The camber follows the shape of the bridge from its jewelled centre to its winged extremities. The entire operation involves grinding and smoothing the surface with a variety of stones and abrasive pastes and then buffing it to a high polish. To meet Vacheron Constantin's standards of finish, this job takes around 11 hours and is done entirely by hand, but it does signify a properly finished movement.
Such is the complexity and level of finish of this horological masterpiece, that it comprises no fewer than 457 parts in a movement only 9.60 mm thick. That explains why the production is limited to just 10 pieces.