New: Greubel Forsey Quantieme Perpetual à Équation in a 5N RG and chocolate coloured gold dial

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Greubel Forsey presents an extension to its QP à Équation with a new model in a 5N red gold millesime with a chocolate coloured gold dial.

We covered the first release in an article here

Original annoucement of the Greubel Forsey Quantieme Perpetual à Équation

An an explanation on how the perpetual calendar works here:

Review of the mechanical computer used in the Greubel Forsey Quantieme Perpetual à Équation

Press Release

QP à Équation

This reinvention of the perpetual calendar integrates the Equation of Time into the perpetual calendar, as well as bringing practical new functions and indications that improve clarity. The priority was to simplify a complete perpetual calendar display and yet make it much easier to set by simply using the bidirectional crown. Despite the numerous indications and functions, Greubel Forsey’s Mechanical Computer is as easy to set as a simple date feature. To meet this technical challenge Greubel Forsey invented a sophisticated coding mechanism: the patented Mechanical Computer. A stack of cams with movable fingers shift the indications on the dial and caseback of the timepiece and the complete mechanism is fully integrated within the movement. The month’s cam changes the month, displayed in a window on the front and also moves the Equation of Time disc on the back. The years’ cam controls the leap year indication on the front and also the millesime and seasons on the back. The development of this coding device not only overturns the conventional way of setting the indications but also displays them simultaneously on both dial and caseback. Just a glance at the calendar display clearly reveals the three in-line windows that clearly indicate the day, the date and the month. The large date makes the calendar extremely legible.

Greubel Forsey QP à Équation

The timekeeping performance comes from Greubel Forsey’s third invention: the Tourbillon 24 Secondes, with its unique fast rotational speed and inclined angle to solve the problem of critical positions of the oscillator in relation to gravity. A 25° angle and the rapid revolution of the tourbillon cage significantly improve the chronometric performance of a system containing only one tourbillon, especially in stable positions. The multi-level chocolate-coloured gold dial of this millesime edition timepiece contrasts harmoniously with the 5N red gold case and underlines the intuitive linear calendar display. Herein lies the happy paradox: it is an ultra-complicated timepiece with complete perpetual calendar, tourbillon and Equation of Time function, however, it is just as easy to use and adjust as a three hands watch. Thanks to the bi-directional correction, it can be easily adjusted in both directions without risk of damage to the movement.

QP à Équation Tourbillon 24 Secondes detail.

The dial side of the QP à Équation indicates leap years, the 24 hours of the day and night, the day of the week, the large date, the month, the hours, the minutes and the seconds, as well as the 72-hour chronometric power reserve. On the movement side, this timepiece displays the Equation of Time with the months, seasons, solstices and equinoxes, as well as the calendar year.

QP à Équation Calendar display with the large Day of the week, large date, month, and a sub-dial for the leap year indicator.

The Equation of Time merits further explanation. Horology seeks to measure time as regularly as possible; however the Earth orbits the Sun in an elliptical path. As the Earth sweeps close past the Sun, the period between successive solar zeniths, or the solar day’s length, changes. This causes the difference between solar time and mean time to vary from a few seconds to as much as 16 minutes during the year. The Equation of Time is the conversion factor between solar and mean time. To read solar time, simply look at the back subdial for the displayed date’s Equation of Time. Greubel Forsey continues to put time to better service; where the caseback of the timepiece is not just there to showcase fine hand finishing, but also provides a new way to tell the time. The most frequently sought calendar information, namely the day, date and month, is displayed on the inline main dial display. Information that is less often required is visible on the back of the timepiece. Thus the two sides show indications that you need to know regularly on the front, and indications accessed less frequently on the back.

QP à Équation case back showing the Equation of Time.

Greubel Forsey QP à Équation In 5N red gold – Millésimé Chocolate-coloured dial

Hand-wound movement with 4 patents Bidirectional perpetual calendar • day, date, month, calendar year, leap year, day/night • equation of time with month, season, solstice and equinox • function selector • Tourbillon 24 Secondes • hours and minutes • small seconds • power-reserve
Movement dimensions • Diameter : 36.40 mm • Thickness : 9.60 mm
Number of parts • Movement : 624 parts • Tourbillon cage : 86 parts • Weight of the cage : 0.37 g
Number of jewels • 75 • Olived-domed jewels in gold chatons
Chronometric power reserve • 72 hours
Barrels • Two coaxial series-coupled fast-rotating barrels (1 turn in 3.2 hours), one of which is equipped with a slipping spring to avoid excess tension
Balance wheel • Variable-inertia with gold mean-time screws (10 mm diameter)
Frequency • 21’600 vibrations/hour
Balance spring • Phillips terminal curve • Geneva-style stud
Main plates • Nickel silver, frosted and spotted with polished bevelling and countersinks, straight-grained flanks, nickel-palladium treatment
Bridges • Nickel silver, frosted and spotted, with polished bevelling and countersinks, straight-grained flanks, nickel-palladium treatment • 4 engraved gold plates, one with the individual number • Flat black polished steel tourbillon bridges • Synthetic sapphire mechanical computer bridge
Tourbillon • Inclined at a 25° angle, 24-seconds rotation • Light alloy cage pillars • Titanium cage bridges • Gold counterweight
Gearing • Involute circle profile • Tangential inclined gear on fixed wheel and profiled teeth on escape wheel pinion
Dial displays • Hours and minutes • Small seconds • 72-hours power reserve on a sector • Day of the week, large date and month • Leap year • Day-and-night with red safety zone • Function selection (perpetual calendar or H/M time adjustment)
Back displays • Equation of time with month, season, solstice and equinox • Calendar year
Case • In 5N red gold with asymmetrical convex synthetic sapphire crystal • Transparent back with asymmetrical synthetic sapphire crystal • Three-dimensional, variable geometry-shaped lugs • Raised polished engraving “QP à Équation” and “Greubel Forsey” on a hand-punched background • Gold security screws • Polished bezel, caseband with hand-finished straight graining • Hand-engraved individual number
Case dimensions • Diameter : 43.50 mm • Height : 16.00 mm
Water resistance of the case • Water-resistant 3 atm – 30 m – 100 ft (standard NIHS 92-20/SN ISO 22810:2010)
Crown • In 5N red gold with engraved GF logo
Dial • Multi-level gold dial, chocolate-coloured • Gold hour markers • Small second, power-reserve • Leap year in polished steel, black treatment • Gold perpetual calendar aperture with polished raised engraving • Gold GF logo
Hands • Hours and minutes in polished gold with Super-LumiNova • Small seconds, power-reserve in polished gold • Leap year in polished steel, black treatment
Strap and clasp • Hand-sewn alligator • 5N red gold folding clasp, hand-engraved with the GF logo


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