When founding Greubel Forsey, Robert Greubel and Stephen Forsey focused all their energy on research and development, with the objective of improving the performance of their timepieces. Their efforts gave rise to many fundamental watchmaking advancements, which took concrete form as inventions, focusing particularly on chronometry.

The Double Balancier – Greubel Forsey’s sixth Fundamental Invention – is a phenomenal timepiece in many ways. Its principle: to drastically enhance timekeeping precision.

Robert Greubel and Stephen Forsey began exploring the Double Balancier – i.e. two fixed oscillators positioned along two different axes at precise predetermined angles – more than ten years ago in order to improve the average timing rate in stable positions. Thanks to the combined effects of the constant spherical differential and the angle of the balances, the effects of gravity are minimised by halving the margin of error and maximising timing precision, a development which resulted in two patents.

Light floods into the timepiece through its sapphire crystal case, which alone required over 900 hours of machining. This showcases the three-dimensional architecture from every angle and reveals the cleverly engineered and enhanced dial and movement with its myriad materials and finishes.

The mechanism reveals itself in its countless details, characteristic Greubel Forsey lines and very high levels of hand finishing performed on each and every component and surface. This pursuit of excellence can be found in even the most unlikely places, including the words central to the Greubel Forsey philosophy, which are engraved around the flanks of the movement itself.

The timepiece is truly brought to life with superior black polishing, satin finishing, circular-graining and superb hand-bevelling (with sharp internal angles). The dial side is certainly worthy of attention with its expertly hand-polished blue gold dial to obtain the celebrated flawless black polish that captures the light. The case back is equally deserving of admiration with its aesthetically balanced openings perfectly integrated into the mainplate.

These apertures highlight the differential bridge – which has been open-worked and integrated into the form of the mainplate – underlining the two regulating organs, which also feature extensive hand-bevelling and black-polished finishes.

This particularly harmonious creation is complemented by two distinctive gold plates engraved with the words “Greubel Forsey” and the individual number of each timepiece, and the setting of olive-domed jewels in polished gold chatons. The timepiece’s transparency is further enhanced by anti-reflective coatings on both sides of the crystals.

This timepiece was inspired by the phenomena of transparency and light. Within a case entirely crafted from sapphire crystal, the spectacular workings of the mechanism are revealed from every angle. The timepiece’s elegant open architecture enhances its components to unveil a stirring, visually striking spectacle.

Every part of the timepiece has been lavished with uncompromising attention to detail. Even the crown is made from sapphire crystal and engraved with the distinctive “GF” mark. It has been carefully developed to ensure user comfort during winding, with its every detail being minutely analysed, from its diameter and thickness to the shape and number of its notches.

The polished white gold hands make it easy to read the time by day and by night thanks to the tips filled with Super-LumiNova®. At 2 o’clock, the dial’s 72-hour chronometric power reserve displays the remaining autonomy provided by the movement’s two barrels.

Last but not least, the case’s distinctive design is punctuated by Greubel Forsey’s eight unique and original screws, which feature a characteristic notch shape and provide additional water-resistance (3 atm, equal to 30 m or 100 ft).The hand-wound movement incorporates 284 components, 30 of which comprise the Constant Spherical Differential.

71 components make up each of the two escapement platforms inclined at 30° angles. Power is supplied by two series-coupled fast rotating barrels, which provide the timepiece with optimum force throughout its 72-hour chronometric power reserve.

The two oscillators have variable inertia balances with gold mean-time screws and beat at 3Hz or 21,600 vibrations per hour. The nickel silver plates and bridges are frosted and spotted, with polished bevelling and countersinks, straight grained flanks and an anthracite grey PVD treatment.

The sapphire crystal case – featuring three dimensional, variable geometry-shaped lugs – measures 47.25 mm in diameter and 13.81 mm in height. The case back, bezel and case body are each entirely machined from a single piece of sapphire crystal.

The timepiece is complemented by a blue rubber strap, elegantly ribbed and inscribed with the exclusive Greubel Forsey signature on the upper surface, while on the inside in relief are the words pivotal to the Atelier’s philosophy. The strap is completed with a Greubel Forsey engraved folding clasp in titanium.

The Greubel Forsey Double Balancier Sapphire with mirror polished blue dial is issued as a Limited edition of just 11 pieces exclusively for the brand’s North American partners.

Technical details

Model: Greubel Forsey Double Balancier Sapphire Limited Edition
Limited edition of 11 pieces in sapphire

Movement

Hand-wound movement with 2 patents
Double Balancier • hours and minutes • small seconds • 4-minutes spherical constant differential rotation • power-reserve

Movement dimensions
• Diameter: 36.40 mm
• Thickness: 8.15 mm

Number of parts
• Movement: 284 parts
• Escapement platform: 2 x 71 parts
• Spherical constant differential: 30 parts

Number of jewels
• 50
• Olived-domed jewels in gold chatons

Chronometric power reserve
• 72 hours

Barrels
• Two 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 wheels
• Variable-inertia with gold mean-time screws (10 mm diameter)

Frequency
• 21’600 vibrations/hour

Balance springs
• Phillips terminal curve
• Geneva-style stud

Main plates
• Nickel silver, frosted and spotted, with polished bevelling and countersinks, straight-grained flanks, grey PVD treatment

Bridges
• Nickel silver, spotted, with polished beveling and countersinks, straight-grained flanks, grey PVD treatment
• Flat black polished steel differential bridges
• Flat black polished gold centre bridge, with polished bevelling and countersinks, straight-grained flanks
• Two engraved gold plates (1x Greubel Forsey, 1x individual number)

Escapement platforms
• Inclined at a 30° angle
• Flat black polished steel, hand-polished beveling and countersinks, straight-grained flanks
• Polished steel pillars
• Flat black polished and barrel polished steel balance wheel bridges

Gearing
• Involute circle profile
• Inclined gear with profiled teeth

Displays
• Hours and minutes
• Small seconds
• 4-minutes spherical constant differential rotation
• 72-hours power reserve on a sector

Exterior

Case
In synthetic sapphire
Diameter: 47.25 mm
Height: 13.81 mm
Bezel, case and caseback machined from a block of sapphire, completely polished
Three-dimensional, variable geometry-shaped lugs
Gold sight ring, engraved on the periphery with the values of the brand, filled with lacquer
Engraving «Double Balancier» and «Greubel Forsey»
Engraved individual number
Water resistance of the case: 3 atm – 30 m – 100 ft (standard NIHS 92-20/SN ISO 22810:2010)
Crown: Synthetic sapphire with engraved GF logo

Dial
Multi-level in gold, blue colour, flat black polished
Differential rotation and small seconds indicators in gold

Hands
Hours and minutes in polished gold, with Super-LumiNova
Small seconds, 4-minutes in polished blued steel
Power-reserve in polished gold

Strap and clasp
Hand-sewn alligator or rubber
Titanium folding clasp, engraved with the GF logo