esigned and conceived with the user in mind, the Traditionnelle Twin Beat Perpetual Calendar was originally launched in 2019. Equipped with a movement featuring two regulating frequencies – a high-frequency Active mode (5 Hz) and a low-frequency Standby mode (1.2 Hz) – and based on two gear trains powered by a series of coaxial barrels, this patented innovation now allows the movement’s autonomy to be extended up to a remarkable 70 days without any loss of timekeeping accuracy, thanks to a high-frequency Active mode (5 Hz) and a low-frequency Standby mode (1.2 Hz). This 70-day power reserve is achieved through an optimization of Calibre 3610 QP, which has resulted in a 5-day gain. A new openworked dial design accentuates its refined character and innovative spirit.

The perpetual calendar is a noble watchmaking complication that fulfils its promise provided the movement is constantly wound. It is distinguished by a cam mechanism that enables the watch’s calibre to strictly follow the specifics of the Gregorian calendar until 2100 without intervention. The calibre’s power reserve is therefore of paramount importance in the absence of an automated watch-winding device. With Calibre 3610 QP, the watchmakers and engineers at Vacheron Constantin have addressed this issue from the user’s perspective, with the aim of extending the autonomy of a perpetual calendar movement without compromising its operation and precision when the watch is not being worn. This gives full meaning to the term ‘perpetual’ in the name of this complication.

In 2019, following four years of research and development, the design of a dual-frequency system integrated into the 3610 QP calibre—one frequency for the wearer’s active phases and the other for the watch’s resting phases—marked a new milestone in power reserve management and, by extension, in the practicality of such a complication. The movement is equipped with two independent gear trains, powered by a series-connected coaxial double barrel. The first, featuring a high-frequency regulation (5 Hz – 36,000 vibrations per hour), ensures that the watch operates with precision in ‘Active’ mode, whilst the second, with a low frequency (1.2 Hz – 8,640 vph), reduces energy consumption during the ‘Standby’ phase.

One of the challenges of this system was to determine how much it would be possible to slow down the oscillation rate of the low-frequency regulator to ensure the longest possible power reserve, without compromising the calibre’s accuracy. With a rate of 1.2 Hz, the watchmakers and engineers at Vacheron Constantin found a balanced compromise, giving Calibre 3610 QP a power reserve of more than two months in ‘Standby’ mode, with a constant amplitude throughout the duration. In “Active” mode, the calibre boasts a four-day power reserve.

To enhance ease of use, Vacheron Constantin’s engineers developed a push-button-operated switching system set in the case-side at 8 o’clock, with a mode indicator displayed by a hand on the dial. This patented system maintains the display of the time and calendar information during the transition between high-frequency Active mode (5 Hz) and low-frequency Standby mode (1.2 Hz), switching instantly from high to low, and vice versa. By stopping one balance wheel to start the other, this causes no interruption in the calibre’s energy chain, thus ensuring a constant display of the time and calendar indications.

Comprising 480 components and measuring just 6 mm thick, the hand-wound Calibre 3610QP has undergone further technical developments since 2019, particularly in relation to its three differentials. To ensure smooth reading of the hours and minutes, a first differential facilitates the transition between the two gear trains.

A second differential is specifically designed to split the energy from the mainspring, channelling it exclusively to the 1.2 Hz gear train, which then powers the 1.2 Hz balance wheel. This balance wheel for Standby mode, recognisable by its larger diameter, is fitted with a hairspring adapted to its rate. Specially developed for this movement, its minuscule thickness of 0.015 mm is far thinner than a human hair.

The third differential is used to indicate the power reserves. As energy storage is provided by a double barrel fitted with two springs, this construction allows, in addition to efficient energy distribution, the display of both power reserves by a single hand in a single counter featuring two scales – set at 12 o’clock on the dial.

To increase the power reserve of Calibre 3610 QP, further research focused on the instantaneously jumping perpetual calendar indications. Generally, this type of display affects the amplitude of the balance wheel, leading to a loss of precision. To address this, Vacheron Constantin’s watchmakers and engineers developed a new double-gear spring-winding mechanism. Operating on a principle similar to that of the first version of the Traditionnelle Twin Beat, this patented system is designed to maximise energy-efficiency. Indeed, it requires four times less torque than conventional instant-jump mechanisms, making the date change much less energy-intensive. It is this optimisation, together with the refinement of the system as a whole – particularly in 1.2 Hz mode – that has enabled the power reserve to be increased by 5 days.

The Twin Beat remains true to the design codes of the Traditionnelle collection, with the rounded shape of its case, slim bezel and fluted caseback. With a diameter of 42 mm, the platinum case measures just 12.3 mm in thickness.

On the dial side, the watch adopts an aesthetic resolutely contemporary in style on different aspect. The sapphire dial, has an engraved and inked railway-track minute track and applied white gold baton hour markers, it comprises two distinct parts. The lower sapphire section reveals the movement’s mainplate, which is sandblasted and treated with NAC galvanic coating. The upper part of the dial is defined by an 18k gold plate, finished in a slate-grey hue and hand-guilloché with a radiating pattern. The hours and minutes are indicated by faceted white gold Dauphine hands.

The same NAC galvanic treatment is applied to the back of the movement. Beneath the bridges, which are hand-bevelled and finished with Côtes de Genève, the mainplate is also sandblasted, while the cover of the imposing barrel is given a circular satin finish. Echoing the two-tone aesthetic of the dial, the reverse of Calibre 3610 QP also offers a striking contrast between the anthracite grey of the fixed components and the golden yellow of the moving parts.

To optimise the readability of the displays, the power reserve, day and month counters have been modified and laser-etched glass gives them a frosted appearance that contrasts with the colour of the movement and the guilloché upper dial. The contemporary aesthetic is enhanced by a strap in textured calfskin with a pin buckle in 950 platinum.

TECHNICAL SPECIFICATIONS

CALIBRE 3610 QP

• Developed and manufactured by Vacheron Constantin
• Hand-wound mechanical
• 32 mm in diameter, 6 mm thick
• 5 Hz (36,000 vibrations per hour), 1.2 Hz (8,640 vibrations per hour)
• 480 components
• 64 jewels
• Active mode (5 Hz frequency): 4 days’ power reserve
• Standby mode (1.2 Hz frequency): 70 days’ power reserve
• Timepiece certified by the Geneva Seal

DISPLAY

• Hours, minutes, instantaneous perpetual calendar, dual-scale power reserve, frequency mode

CASE

• Platinum 950
• 42mm diameter, 12.3mm thick
• Transparent case back with sapphire crystal
• Water resistance tested to a pressure of 3 bar (approx. 30 metres)

DIAL

• Inner section in hand-guilloché 18K gold, slate grey finish
• Transparent sapphire crystal
• Hour markers, hour and minute hands in 18K white gold
• Power reserve and frequency mode hands in 18K yellow gold with black PVD treatment
• Date and month hands, sandblasted and rhodium-plated

STRAP

• Black technical calfskin with a textured finish, hand-stitched calfskin lining with red thread, folded edges

CLASP

• 950 platinum pin buckle