Zenith’s 160th anniversary celebration continues with the Defy Zero G, a sapphire-cased watch equipped with the brand’s latest generation, gimbal-like “Gravity Control” escapement module.

Available in either clear or deep blue sapphire – both with a lapis lazuli dial – the 46 mm anniversary model is a literal showcase for the innovative cal. 8812 S, which features a gimballed escapement platform that keeps the balance wheel in a horizontal position at all times. Originally developed in 2008 and refined in 2018, the Zero G mechanism is a modern homage to Zenith’s legacy in competitive chronometry and marine navigation.

Initial thoughts

Today, the Zenith brand is synonymous with the El Primero chronograph movement, launched back in 1969. But outside of that, the manufacture has always been a major force in Swiss precision watchmaking. For decades the brand regularly took home the top prizes at chronometry trials from Neuchâtel and Teddington. Zenith already paid tribute to its past success in competitive chronometry with the G.F.J. cal. 135, which also features a lapis lazuli dial, but it’s reassuring to see the brand made time to bring out one of its more recent developments for its anniversary year.

While the days of chronometry trials are long past, Zenith has still managed to make a name for itself when it comes to the accuracy of wrist-worn timepieces — at least theoretically. Back in 2008 the brand unveiled a curious mechanism, with the escapement fully pivoted in a gimbal-like contraption that always kept the oscillating organ horizontal with the ground. 

Reminiscent of Zenith’s heritage as a maker of marine chronometers, which were suspended in gimbals in protective wooden boxes, the original system was bulky and more of a proof-of-concept. But a decade later the concept was refined, resulting in a compact new design that required just 30% of the volume of the original. For horology aficionados, a mechanism that automatically adjusts the oscillating regulator to a gravity-impervious position is an interesting proposition; it’s somewhat like a tourbillon but in fact serves essentially the opposite function.

The watches themselves are large and loud, with full sapphire crystal cases in the Defy’s bulky silhouette. Save for the eccentric engineering within, the anniversary models stick to the standard Defy aesthetic. While both models look appealing, the clear version seems slightly more impressive, looking more distinct from the blue ceramic Defy launched earlier this year.

The well-constructed cal. 8812 S does a good job filling the large case, and the intriguing behavior of the gimballed escapement is the main attraction of the watch. Fortunately, the manually wound 5 Hz calibre is open worked to let in plenty of light and allow the mechanism to been seen from all sides.

The anniversary model serves as a good opportunity to showcase Zenith’s innovative watchmaking, but the large size of 46 mm and lofty price of CHF200,000 temper the appeal. On the flip side, sapphire-cased watches are always expensive, and the production run is quite small – just 10 pieces each –  which helps justify the pricing to some extent.

The clear sapphire case version

Sapphire dress

Though sapphire crystal wristwatch cases are a relatively recent development, the transparency of the material is a natural fit for an object like a watch that contains an elaborate mechanism within. This has always been the case (no pun intended) and there are examples of sapphire-cased watches dating back centuries. Machining such a hard mineral is no easy feat, especially when considering the many facets of the Defy case, which are rendered with aplomb. Interestingly, both the angular case with its raised bezel and the case back are cut from sapphire, making for an unusual habillage. 

The case has a 46 mm diameter, which is large by any standard. Admittedly, the movement within is plenty large in size and perhaps the tolerances of sapphire milling have their own effect, but the size is definitely on the larger size. The case is water resistant to 30 m, which is minimal but acceptable given the special nature of Zero G.

Precious cut dial

In both models, the dial is almost integrated with the movement. Much of the watch face is left completely open to showcase the fascinating Gravity Control module, while the upper half is covered by the actual dial. 

In an extravagant touch for a celebratory occasion, the dial itself is cut from lapis lazuli, a semi-precious stone with a natural blue colour and glittering occlusions. The main dial features a railway minutes track, while the blocky indices and hour and minute hands are a call back to Zenith’s historic designs.

There is also a small seconds sub-dial integrated with the primary time display and a discreet power reserve indicator at three o’clock that counts down the 50-hour power reserve.

A laudable caliber

Regardless of case colour, the Zero G is powered by the Zenith cal. 8812 S, an innovative and obviously unique movement. It features a proprietary escapement module that pivots freely, weighted to keep the sprung oscillator parallel to the ground at all times. In practice, the idea is to nullify the deleterious effects of gravity on the movement’s positional performance, hence the Zero G moniker.

Back when it was first launched, the gimbaled regulator was large enough that it required a domed bubble in the sapphire crystal so that it could rotate and balance freely. Some ten years later, Zenith has refined the concept so that it can rotate within a smaller footprint; no bubble is needed this time. 

Without question, the main talking point is the Gravity Control escapement module. Made possible by a very clever assembly of differential gearsets, the module has three degrees of rotational freedom, thus it can always orient itself in the desired position with respect to the ground.

This action works thanks to a counterweight fixed underneath the escapement platform, which always keeps the sprung balance oscillating on a plane parallel to the Earth. As such, any poising defects (related to the hairspring’s unequal breathing or the balance itself) have no influence on the rate.

The system is very intricate, with the module itself having no less than 139 pieces. Naturally, the mechanism serves much the same purpose as the cardan fixtures that kept marine chronometers level, always adjusting for the ship’s wave-induced rocking. 

Despite its magnificent complexity, the escapement in the cal. 8812 S does disappoint slightly in one regard; the oscillator itself is not free-sprung. Since Zenith went all this way to make a reliable, self-adjusting escapement module in search of ultimate accuracy, the brand could have also equipped it with a free-sprung balance. While the Gravity Control system eliminates some of the positional errors that can be introduced by the curb-pin regulator, a free-sprung balance would help prevent the rate from drifting over time. The system does, however, benefit from a silicon escapement, which reduces frictional losses and fares well in terms of magnetism resistance.

Watches like this that focus on a singular technical achievement rarely exhibit artisanal finishing. And while the cal. 135 in the G.F.J. was dressed up with luxurious anglage, the cal. 8812 S is finished in Zenith’s typical, industrial manner, though the blue treatment livens things up.

Key facts and price

Zenith Defy Zero G Sapphire
Ref. 04.9000.8812/51.R584 (transparent sapphire)
Ref. 04.9003.8812/51.R584 (blue sapphire)

Diameter: 46 mm
Height: Not available
Material: Blue or translucent sapphire
Crystal: Sapphire
Water resistance: 30 m

Movement: Cal. 8812 S
Functions: Hours, minutes, small seconds, power reserve
Frequency: 36,000 beats per hour (5 Hz)
Winding: Hand wind
Power reserve: 50 hours

Strap: Blue alligator strap with folding buckle

Limited edition: 10 pieces in blue sapphire and 10 in translucent sapphire
Availability: At Zenith boutiques and retailers
Price: CHF200,000 excluding taxes

For more, visit Zenith-watches.com.