Zenith: the factory, the fast beat and the saved tools

1865: precision begins with the workshop

Georges Favre-Jacot established his watchmaking enterprise in Le Locle in 1865. His ambition involved bringing different watchmaking trades into a coordinated manufacturing site. Before studying a movement, it is worth picturing that organisation: components have to arrive with consistent dimensions, in the correct sequence, ready for assembly and adjustment. A successful watch is also the result of a successful production system.

Zenith’s account links the company’s eventual name to its celebrated Zenith calibre, recognised at the Paris exhibition of 1900. The story is more useful as a connection between product and identity than as a claim that the factory invented industrial watchmaking single-handedly. Manufacture describes how work is organised; it does not eliminate the skill of individual craftspeople.

Evidence: Zenith: Georges Favre-Jacot

Calibre 135: timing trials before El Primero

The calibre 135 supplies an essential counterweight to the famous chronograph. Produced from 1949 to 1962, it existed as a commercial movement and as the 135-O prepared for observatory competitions. Zenith credits the competition version with five consecutive first prizes in the wristwatch category at Neuchâtel from 1950 through 1954. Those results belong to specially prepared movements and their regulators, not automatically to every watch carrying the brand.

A chronometer concerns tested timekeeping performance; a chronograph measures an interval. The distinction explains why a simple-looking watch can have an important precision history. The modern G.F.J., introduced in 2025, revisits the 135’s architecture through a re-engineered movement. It should not be mistaken for an untouched competition calibre from the nineteen-fifties.

Evidence: Zenith: G.F.J. and the historical calibre 135

1969: what the fast beat actually means

Zenith announced El Primero on 10 January 1969. Its integrated automatic chronograph combined self-winding with an interval timer, rather than treating those functions as mutually exclusive. Integrated means that the chronograph is designed into the movement’s overall construction. The column wheel coordinates the chronograph’s operations; the clutch connects or separates the timing mechanism from its driving train.

The familiar frequency of 36,000 vibrations an hour equals ten beats each second, or five complete oscillations. That creates a basis for tenth-second interval timing, not a guarantee that a watch gains or loses only one tenth of a second per day. Other automatic-chronograph projects also reached the public in 1969. Announcements, production readiness and retail availability are different milestones, so a single unqualified “first” obscures more than it explains.

Evidence: Zenith: manufacture timeline, Zenith: Chronomaster 2 and calibre 3600 technical release, TAG Heuer: official historical timeline

Charles Vermot: saving the ability to make a movement

According to Zenith’s account, management decided in 1975 to stop producing El Primero as the industry shifted towards quartz. Watchmaker Charles Vermot preserved the plans and production tools in a concealed part of the manufacture’s attic. They later helped the company resume making the movement. The memorable object in this story is therefore not a finished watch but a collection of equipment that might otherwise have disappeared.

Treat the account as the house’s retrospective history, without adding imaginary conversations or a dramatic last-minute rescue. Its broader lesson is practical: drawings alone do not capture every fixture, tool and learned production method. Keeping those resources together can preserve an industrial capability that would be costly and difficult to reconstruct.

Evidence: Zenith: Charles Vermot and the manufacture attic

Chronomaster: learn the display before timing anything

The Chronomaster Original carries forward the round-case language and overlapping coloured counters of the 1969 A386. In the modern calibre 3600 version, the central chronograph hand makes a complete turn in ten seconds. Its circuit therefore cannot be read like the usual sixty-second sweep. The graduations, counter labels and the actual motion of the hand must be understood together.

This makes a useful learning exercise: time a short interval, stop the chronograph, and identify where whole seconds and their fractions are shown. Then compare the result with an older El Primero display. Shared ancestry does not imply identical indications. The cited modern model adds stop-seconds and a stated sixty-hour power reserve; those specifications should not be projected backwards across every generation.

Evidence: Zenith: Chronomaster Original and El Primero 3600

Defy: another way to be a Zenith

1969 also brought the Defy A3642, whose angular case and fourteen-sided bezel offered a different visual proposition from a round chronograph. The 2022 Revival A3642 revisited that design, including the open-link ladder bracelet associated with the original. The result is a useful reminder that Zenith’s design history is not confined to three overlapping counters.

Study the case from the side as well as from above. Facets, bevels and the relationship between bezel and bracelet create the impression of strength before the mechanism is visible. That impression is design, not a substitute for a water-resistance specification. An original A3642 and its modern revival also require separate checks of movement, materials, dimensions and service condition.

Evidence: Zenith: the 1969 Defy and Revival A3642, Zenith: Defy Revival A3642 technical sheet

Care: preserve function and understand the intervention

Choose the operating instructions for the exact calibre before using the crown, date corrector or chronograph. Zenith separates its online manuals by generation, a sensible warning against assuming that a familiar-looking watch operates exactly like another. If the reference is uncertain, establish its identity before experimenting with the controls.

A complete Zenith service includes disassembly, cleaning, lubrication, adjustment and functional tests, with gaskets replaced and water resistance checked to the watch’s specifications. For an older example, ask what replacement of hands, dial or exterior components would involve before approving restoration. A service record explains work performed; a handsome case alone does not establish internal condition. Continue with the chronograph, chronometer and servicing guides to connect the history with everyday observation.

Evidence: Zenith: complete maintenance service, Zenith: operating instructions and user manuals

Selected chronology

Dates describe the stated event or generation, rather than every watch in a family.

1. 1865
   Favre-Jacot establishes his Le Locle watchmaking enterprise.

   Evidence: Zenith: Georges Favre-Jacot

2. 1949–1962
   Calibre 135 is produced in commercial and observatory-trial versions.

   Evidence: Zenith: G.F.J. and the historical calibre 135

3. 1969
   El Primero is announced in January; the Defy A3642 also appears that year.

   Evidence: Zenith: manufacture timeline, Zenith: the 1969 Defy and Revival A3642

4. Mid-1970s
   Vermot preserves El Primero production resources during its interruption.

   Evidence: Zenith: Charles Vermot and the manufacture attic

5. 2022 / 2025
   Revival A3642 revisits the Defy; G.F.J. reinterprets calibre 135.

   Evidence: Zenith: the 1969 Defy and Revival A3642, Zenith: G.F.J. and the historical calibre 135