Surpassing other watchmakers, Zenith has 2,333 chronometry prizes under its belt. Produced from 1949 to 1962, the iconic Calibre 135-O alone earned the maison 235 prizes.
A re-engineered version of the record-breaking movement now powers the platinum G.F.J. -- one of Zenith's 160th anniversary timepieces unveiled at Watches and Wonders Geneva 2025.
The initials, which reappear on the crown, dial, caseback and pin buckle, refer to founder Georges Favre-Jacot.
In 1865, at the age of 22, he established a workshop on Rue des Billodes in Le Locle. Participation in observatory trials began in 1897 -- the same year of the launch of his flagship Calibre Zenith that later became the company's name.
"Taking part in these competitions was a natural extension of a commitment to accuracy and precision. It was the path chosen by Zenith's founder, Georges Favre-Jacot, to prove the manufacturing system he pioneered in the world of Swiss watchmaking would produce reliable, more perfect watches," said head of heritage Laurence Bodenmann.
Inspired by American industrialisation, Favre-Jacot revolutionised Swiss watchmaking through a vertical integration that brought all the skills under one roof.
The entrepreneur even made his own tools and machines, ran a stone quarry, set up a brickwork as well as a foundry and printing house. In just a few years, his workshop became the largest manufacture in the Neuchâtel mountains, spanning across an area of 9,300m² and comprising 18 buildings.

The commemorative G.F.J. is a limited edition of 160 pieces.
His vision spurred the development of the perfect watch, and the company momentously took home the Grand Prix for technical and aesthetic excellence at the 1900 Paris Exposition.
The mid-20th century saw the golden age of chronometry competitions and Zenith as a key player with the development of the Calibre 135-O and its commercial variant.
"Observatory trials were highly significant for watchmakers, serving as the ultimate test of a movement's precision and technical quality. These competitions were more than just a pursuit of accolades; they represented a benchmark of excellence, with results that enhanced a brand's reputation and credibility," said Bodenmann.
Named after its dimensions -- 13 lines (30mm) and 5mm thickness -- the Calibre 135-O was specifically developed for competitions at the observatories of Neuchâtel, Geneva, Kew Teddington and Besançon.
"Calibre 135-O became the most awarded movement, including a remarkable series of five consecutive wins at the Neuchâtel Observatory from 1950 to 1954," noted Bodenmann. "What sets it apart is its extra-large balance wheel, which brings more inertia and shapes its entire architecture in a way never seen before. That is what makes it an icon in the world of watchmaking."

The re-engineered Calibre 135 delivers a power reserve of 72 hours.
Providing a power reserve of 40 hours, vintage calibres from these winning years were restored and decorated by master watchmaker Kari Voutilainen for a collaboration with Zenith and Phillips in association with Bacs & Russo.
After the restoration for the exclusive 2022 edition, Zenith has upgraded the Calibre 135 for the commemorative G.F.J. with an increased power reserve of 72 hours. Certified by COSC, the manually-wound movement is regulated to be precise within +/-2 seconds per day.
Based on the dimensions and architecture of the legendary calibre, modifications include a new gear train featuring an optimised tooth geometry for enhanced efficiency while the offset centre wheel creates space to accommodate the oversized balance wheel that improves both precision and stability.
The signature double arrow-shaped regulator allows for precise adjustment, while a stop-second mechanism has been added to set the time to the exact second.
The meticulously-finished components include bridges with a "brick" guilloché, inspired by the façade of the Zenith Manufacture.
Likewise, the dial is designed with a brick guilloché pattern on the outer ring with faceted white gold hour markers and a discreet minute track of 40 white gold beads applied by hand.

Dial of the G.F.J. with a three-part construction and a brick guilloché pattern on the outer ring.
The three-part construction of the blue dial creates a sense of depth. The central part crafted from Lapis Lazuli shimmers with gold-coloured pyrite flecks evoking a starry sky while the oversized small second counter at 6 o'clock harmonises in mother-of-pearl.
All in all, the design of the G.F.J. captures the essence of the 1950s, presented in a 39mm platinum case with a stepped bezel and curved stepped lugs, and matched with a leather strap or platinum bracelet.
"The 1950s were a time of bold graphic exploration and innovation -- designers were pushing boundaries, creating lines that felt both fresh and timeless. The goal was always to create something that would stand the test of time, appealing across generations. In 2025, Zenith is taking this idea even further, refining and modernising this 'forever design' for the next generation," said Bodenmann.
Released in a limited edition of 160 pieces, the G.F.J. is available for pre-order exclusively from Zenith's physical and online boutiques, as well as through authorised retailers worldwide.

Calibre 135 features a brick guilloché decoration, inspired by façade of the Zenith Manufacture.

Zenith's award-winning calibre portrayed in an ad from the 1950s.