We ran review of the Greubel Forsey Invention Piece 3 yesterday, and covered the 6 inventions of Greubel Forsey. But there is a seventh: the Invention 7 is the Computeur Mécanique or Mechanical Computer.
The 7th Greubel Forsey invention
We almost missed it, but a kind email by Emmanuel Vuille, CEO of Greubel Forsey reminded me that I might have forgotten the Invention 7. OK, admission time: I did forget.
Called the Computeur Mécanique, French for Mechanical Computer, the invention is a unique and exclusive mechanism, for which several patent applications have been filed.
The Greubel Forsey Invention 7 is a mechanical computer which is able to calculate and show in a display numerous different measurements. These are coded in the stack of discs and wheels arranged coaxially. The Invention is able to be programmed to automatically display all the indications of the perpetual calendar: the day, date, month and four digit year as well as the seasons, the equinoxes, the solstices, and the equation of time. For example, the differences during a leap year are taken into account and managed by the specific programming of one of the coded elements.
The inspiration for a mechanical computer comes from the systems used in large astronomical clocks since the end of the 15th century. These systems manage and coordinate the information around key dates, which may include ecclesiastical dates like Easter in relation to astronomical data.
The Mechanical Computer provides the means to measure the difference between solar time (known as sundial or true solar time) and mean time which is conventionally fixed and divides the day into 24 equal parts. A solar day changes throughout the year, due to the Earth’s elliptical orbit around the Sun, but mean time remains the same year round. The difference between the two time scales can be as high as +16 minutes in November and -14 minutes in February.
This invention is realised in a watch: though not officially designated Invention Piece 7, is called the Quantième Perpetual à Équation: a watch which displays the Perpetual Calendar with Equation of Time. While a watch showing a full perpetual calendar with equation of time functions are not unique, they are extremely complicated, and as a result rather rare. The Breguet 3477 is one example. Vianney Halter’s Janvier Lune et Soviel is another. But what is interesting on the Greubel Forsey QP à Équation is that all the indicators are centrally coordinated via the mechanical computer.
The watch shows the full calendar display: Day, Date, Month, Leap Year, a 72 hour power reserve indicator and a 24 hour dial with red markings when the watch should not be adjusted as it may damage the computer and perpetual calendar elements. On the back, more indicators:
Other than the beautifully frosted plate with its shiny anglage and details like the specular polished tourbillon bridge, the jewels gleaming in their gold chatons, of note from the back is the Equation of Time indicator.
This is shown by the two overlapping coloured sapphire plates driven by the Mechanical Computer. The Mechanical Computer rotates them independently to show the time differences as it changes throughout the year. The top plate carries the equation of time, and a second sapphire disk, placed directly below contains the indications for the seasn, solstice, and equinox.
Of course, as this is a Greubel Forsey watch, it is equipped with a 24 second tourbillon inclined at 25°. The watch is now available, though we were told, quantities are very limited, at a very cool S$1,075,350 with GST in Singapore. This makes the Quantième Perpétuel à Équation the most expensive Greubel Forsey in the market, with the exception of the Art Piece and bejewelled pieces.