For its latest masterpiece, Greubel Forsey is revisiting and merging its earlier work. Shades of the Double Tourbillon 30° and Quadruple Tourbillon (from 2004 and 2005, respectively) and the GMT (from 2011) can be found in this year’s GMT Quadruple Tourbillon.
The result is a hefty piece, measuring 46.5mm in diameter and nearly 17.5mm thick. The aesthetic spectacle is true to the inimitable, asymmetric Greubel Forsey style: the offset time indicator and rotating titanium globe with universal time function seem to bulge out the side of the case, the tourbillons are fully openworked, and the exposed movement plates are frosted nickel silver. There are additional indicators for power reserve, second time zone and small running seconds, while the back reveals a rotating cities disc with day/night indications. Each individual element seems workmanlike and functional (if exquisitely finished), but when taken as a whole the timepiece is full of visual depth and complexity.
Greubel Forsey has always taken the tourbillon seriously, never forgetting that it was originally invented to improve timing accuracy and not just an animated treat. The quad-tourbillon system in this watch involves two pairs of tourbillons, each modelled after the Double Tourbillon 30°. This involves one cage angled at 30 degrees rotating once per minute inside a second upright cage rotating at once in four minutes. The intent is to compensate for timing variations that arise due to the different positions a wristwatch adopts while worn. (A single tourbillon, in contrast, was meant to do the same for a pocket watch that would mainly be carried in a single, stable position throughout the day and is therefore not so applicable to a wristwatch.) The two pairs of tourbillons, which otherwise operate independently, are linked with a spherical differential. This outputs the average of the two, resulting in an even better error compensation and improved chronometric performance. The hand-wound calibre has a total of 705 parts and boasts of three patents—a fine example of the sort of consummate technicality that one expects of the inventor-watchmakers, Robert Greubel and Stephen Forsey.
The GMT Quadruple Tourbillon is released as a run of 66, of which 11 will be in white gold cases and individually numbered on a plate in the centre of the dial.
