This year for Only Watch 2023, two of the most exciting young independent watchmakers, Petermann Bédat and Théo Auffret have come together to create the Chronomètre d’Observatoire Ref: 1342. This marks the debut participation of both brands in the charity auction, with the one-of-a-kind timepiece housing an artisanal version of the legendary Zenith caliber 135 from the 1950s.

Comprising of Gaël Petermann and Florian Bédat who first met at watchmaking school at the age of 15, Petermann Bédat has introduced two impressively constructed and finished watches since their debut in 2020, beginning with the 1967 Deadbeat Seconds and then the incredible Monopusher Split-Seconds Chronograph Ref. 2941. Théo Auffret’s journey, on the other hand, started with a victory in the F.P. Journe Young Talent Competition in 2018 . He went on to introduce the Tourbillon à Paris in a subscription series of five pieces and eventually, the Tourbillon Grand Sport in a series of four pieces. More recently, the Parisian watchmaker embarked on a joint venture with French watch entrepreneur Guillaume Laidet and launched the Argon Space One, an accessible high-concept watch that was an intriguing departure from his own traditional style.

Among the 62 watches designed for Only Watch, the Chronomètre d’Observatoire Ref: 1342 stands out for its remarkable restraint, as is characteristic of precision timekeepers built for the sole purpose of honors in observatory trials. Encased in steel, it is classically proportioned, measuring 38.3mm in diameter with a thickness of 10.8mm. The case is fully polished and accented by gently curved lugs that have been individually soldered to the case.

The sector dial, made of solid silver, has been thermally treated to achieve its pale silver hue which serves as a contrasting backdrop for the rose gold indexes and hands. The simplicity of the dial sets the stage for the beautifully crafted hands, which exhibit a unique form and thickness that can only be achieved by hand. Each of which is attached to its own hub that has been bevelled and polished. The minute markers and small seconds subdial are engraved and filled with black lacquer, with the only other touch of colour coming from the blued seconds hand.

On the back is the Zenith 135 based caliber that has been heavily reworked to demonstrate the highest level of craft. The caliber 135 was originally developed in 1945 by watchmaker Ephrem Jobin, who was prompted by a challenge from the technical director of Zenith at the time, Charles Ziegler, to develop a chronometer movement for honours in the observatory time trials. The movement was designed with a large mainspring barrel for isochronism and a power reserve of 40 hours and a massive 2.5Hz balance wheel. To accommodate the size of the balance and to reduce thickness, the second wheel is offset from the central axis and drives a pinion in the centre. From 1949 to 1962, the calibre was produced in two distinct iterations: a commercial version and a second variant, the 135-O designed exclusively for participation in chronometry competitions at the observatories of Neuchâtel, Geneva, Kew Teddington, and Besançon, eventually amassing over 230 honours.

The main plate and bridges in the Ref: 1342 were made from scratch using German silver by the Fleury Manufacture, a small independent workshop based in the heart of Geneva and finished by Petermann Bédat and Théo Auffret while the wheel train and screwed balance were taken from the original Zenith 135 calibre. The bridges are decorated with Théo’s signature “charbonnage” or coal finishing, which he has employed in his tourbillon watches. According to Théo, it is a traditional Parisian technique that was commonly used in the first half of the 19th century. The surface is cleaned and smoothed. Then the watchmaker uses a charcoal block and oil to generate undulating patterns by carefully rubbing the surface.

While the original Zenith 135 had a separate bridge for the third and fourth wheels, the Chronomètre d’Observatoire Ref: 1342 features a single bridge for the barrel and gear train, which has been beautifully refined to form four internal angles. The screws and jewels sit in wide, mirror-polished countersinks. The hub of the crown wheel has been black-polished while the ratchet wheel has a deep, polished recess. Notably, it uses an attractive and elaborate click setup designed and produced by Théo, where the click spring coils around the click, providing the resistance to the click index. The balance is equipped with an overcoil hairspring and the original index regulator has been replaced by a beautifully finished swan-neck regulator made by Petermann Bédat. As is characteristic of Petermann Bédat watches, the balance assembly has a beautiful traditional design with a wide black-polished circular hub that is held in place by two screws to retain the cap jewel. The hairspring is attached to traditional kidney-shaped stud piton that is finely finished like the rest of the movement. In short, this is the finest execution of one of the finest hand-wound chronometer wristwatch movements in the history of watchmaking.