This exquisite keyless pocket watch with a large hunter case in 18K gold features a Guillaume balance. It comprises a carillon minute repeater with three hammers striking three gongs, a perpetual calendar with leap year and moon phase display, a split-seconds mono-totalizer chronograph and an alarm. It was sold to Count Guy de Boisrouvray in 1948.
Until 2015, this grand complication was the third most complicated watch ever produced by Vacheron Constantin. Count de Boisrouvray, a cousin of Prince Rainier III of Monaco and a far-sighted collector, was married to Luz Mila Patino, daughter and heiress of one of the richest men in the world —Bolivian tin magnate Simon Patino. This fortune allowed the couple to assemble a collection of artworks of all kinds including Fabergé pieces, fabulous jewellery, and paintings by Impressionists and other great masters. Naturally, Count de Boisrouvray wanted a watch of equivalent beauty.
The movement with perpetual calendar and split-seconds chronograph is not only highly complicated but also features a meticulously crafted escapement that guarantees its precision. The Guillaume balance is equipped with a setting screw in gold and platinum, whose properties render it insensitive to temperature variations and magnetic fields. The movement is also equipped with a regulation system that guarantees precision in a uniquely effective manner. All these elements were uncommon in the complicated watches of the period. Several features of the complications of this watch place it at the pinnacle of exceptional timepieces. For example, the alarm requires a specific mechanism that is integrated into the striking movement; it has an additional hand for setting the alarm time. Including the alarm hand, a total of five hands are mounted on the central axis, a rare thing in itself. Elsewhere, the carillon minute repeater requires a special construction comprising three gongs struck by three hammers to sound a peal of three notes when activated.