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Zenith Chronomaster Open 39.5mm
Ref. 18.3300.3604/69.C922
Sits in Zenith’s upper tier here — more premium than three quarters of the Zenith watches we list, which start at £7,000.
Price range £7,000 to £28,000 across 44 Zenith watches in stock.The El Primero movement that Zenith hid in a drawer rather than abandon during the quartz crisis became the calibre every serious chronograph reference for the following decade was measured against. The Chronomaster Open makes its case for that reputation visually: a circular aperture cuts into the upper left of the silver dial to expose the balance assembly in motion, and beneath the open mainplate and bridges the silicon escape wheel and pallet fork run without lubrication, an engineering choice with a genuine maintenance argument behind it. The central chronograph hand completes a full sweep in ten seconds, which means each division marks a tenth. At 39.5mm with a lug-to-lug of 45.2mm, this sits closer to the wrist than its case height of 13.1mm might suggest on paper — the short lugs keep the watch from cantilevering, and on most wrists it will not catch on a cuff. The solid rose gold reads warmer against the matte silver dial and the traditional tricolour sub-registers than a photograph tends to show. The navy calfskin sits comfortably against it, and the rose gold triple-fold deployant closes the same way the case is built — as though the detail matters.
- Reference
- 18.3300.3604/69.C922
- Brand
- Zenith
- Collection
- Chronomaster
- Case size
- 39.5mm
- Case thickness
- 13.1mm
- Lug width
- 20mm
- Case material
- Rose gold
- Case shape
- Round
- Dial
- Silver
- Crystal
- Sapphire
- Movement
- Automatic
- Calibre
- El Primero 3604
- Functions
- Chronograph, Small seconds, Skeleton dial
- Water resistance
- 100m
- Bracelet / strap
- Leather strap
- Strap colour
- Blue
- Clasp
- Deployant clasp
- Lume
- Luminous
- Retailer
- Goldsmiths
Additional specifications
- Lug-to-lug
- 45.2mm
- Power reserve
- 60 hours
- Warranty
- 2 years
Learn more about Zenith
Georges Favre-Jacot founded Zenith in Le Locle in 1865, aged twenty-two, with an idea that was radical for the Swiss industry: bring every trade needed to make a watch — movement, case, dial, hands — under one roof and one management. The integrated manufacture was largely his invention, and the Le Locle site he built is still in use.
The approach produced results at observatory trials, where Zenith accumulated more precision awards than any other manufacture. The name itself came from a calibre Favre-Jacot considered the summit of his work.
Its defining achievement is the El Primero of 1969, developed over seven years and announced in the same year as the Heuer-Breitling consortium's Calibre 11 and Seiko's 6139. It was an integrated automatic chronograph beating at 36,000 vibrations per hour, allowing measurement to a tenth of a second — a frequency almost nothing else matched for decades.
It nearly did not survive. When American owners ordered the mechanical tooling scrapped during the quartz crisis, a watchmaker named Charles Vermot hid the plans, presses, and cams in a walled-off attic. When demand for mechanical chronographs returned, Zenith could restart production because of him. Rolex used the El Primero in the Daytona from 1988 to 2000.
LVMH acquired Zenith in 1999.
- 1865
- Georges Favre-Jacot founds the integrated manufacture at Le Locle.
- 1969
- The El Primero automatic chronograph debuts at 36,000 vph.
- 1975
- Charles Vermot hides the El Primero tooling from destruction.
- 1988
- Rolex adopts the El Primero for the Daytona.
- 1999
- Acquired by LVMH.
Manufacturer’s guarantee
Your new watch
Frequently asked questions, and things you should know about this watch
Can I swim with it?
Yes. At 100m it is rated for swimming and snorkelling, though not for diving.
Will the glass scratch?
Unlikely. Sapphire is second only to diamond in hardness and shrugs off everyday marking.
Does it need a battery?
No. It is automatic — the motion of your wrist winds it, and there is no cell to replace.
How long does it run for when it's not worn?
About 60 hours fully wound — enough to survive a night off the wrist, but not a full weekend.
What size strap does it take?
20mm. Any strap of that width will fit, and on most modern watches quick-release bars make the swap a two-minute job with no tools.
Will it fit my wrist?
Lug-to-lug is 45.2mm, which suits wrists from roughly 16cm (6¼ inches) upward.
Lug-to-lug decides fit more than case diameter does.
Is it a men's or women's watch?
Listed as men's, though at 39.5mm it sits in the range that suits anyone.
Cheapest place to buy
Goldsmiths is the only UK retailer we track stocking this reference, so there is nothing to compare it against today.
Who are Goldsmiths?
Goldsmiths has been selling watches in Britain since 1778 and is part of the Watches of Switzerland Group, which is listed on the London Stock Exchange. They are an authorised dealer, so a watch comes with the manufacturer’s own warranty.
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