Greubel Forsey QP À ÉQUATION in 5N Red Gold Millesime with Chocolate Gold Dial

Following the GPHG (Grand Prix d’Horlogerie de Genève) award for the best Calendar Prize, Greubel Forsey presents its QP à Équation in a 5N red gold millesime with a chocolate coloured gold dial.

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.

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.

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 two sides showing 15 indications 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.

Its case back showcases fine hand finishing, and 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.

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.

Technical details

Model: Greubel Forsey QP à Équation 5N Red Gold Millésimé Edition with Chocolate-coloured Dial

Movement
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
Diameter: 43.50 mm
Height: 16.00 mm
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
Water resistance of the case: 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