It’s one of the most common mistakes made by consumers when trying to get their heads around watch jargon – muddling a chronograph with a chronometer. The former, as the Greeks would have it, is a ‘time writer’, a device that can capture the timing of a single event. So a stopwatch for fancy people. The latter is a watch powered by a movement that has been independently certified for accuracy by some of the most pedantic people in the world – the boffins at the Contrôle Officiel Suisse des Chronomètres, or COSC for short.
These guys are pretty fastidious. They take movements, uncased and usually supplied by brands, and then test them for 15 days in five different positions and in a range of temperatures, measuring them for accuracy as they go. If at the end of said test they are, on average, accurate to within -4 to +6 seconds a day, they are deemed worthy of chronometer status.
What does this mean? Depends on who you ask. While around 6 per cent of watches leaving Switzerland carry the chronometer designation, these days, a lot of companies make watches with movements accurate enough to be chronometer-certified, but don’t bother getting them tested, either because they want to keep the cost down – on a mid-range watch, you can expect to pay circa £200 extra for a watch with the word chronometer on the dial over a standard mechanical – or, more likely, because they don’t think the standard is tight or exclusive enough. Patek Philippe, for example, self-certifies with the Patek Philippe Seal, which assures buyers of accuracy to -3 to +2 seconds a day.
Others are more convinced. Most Rolex watches are chronometer-certified, although the company would like you to know that its in-house suite of calibres includes units such as the 3235, which, it says, is accurate to -2 to +2 seconds a day, after casing. Omega is another fan, although it now qualifies its watches as ‘Master Chronometers’ to certify that not only have they been through COSC, they’ve also been ok-ed by METAS, another independent organisation that guarantees Omega’s movements retain their chronometer-level performance even when cased and submitted to a barrage of tests for things such as anti-magnetism.
Ultimately, what you get with chronometer status is an extra degree of reassurance that your watch is at least going to keep you vaguely on time, and a bit more Swissness on your wrist. The Swiss boast of superlative accuracy is generally over-egged, or at least anachronistic – a mechanical watch can’t compete with a solid battery-powered quartz on that front, and certainly not a GPS-enabled smartwatch.
But then let’s allow ourselves to marvel at a mechanical object that beats at 28,800vph and can do that accurately to within seconds a day. And besides, why would you want a watch any more accurate? Life is exacting enough as it is.
The big players in the world of chronometers are Rolex, Omega and Breitling, with a supporting cast of around 60 brands each year, including Chopard, Panerai, TAG Heuer and Tissot. Although for now, details of how many of each pass the test are no longer available. As of last year, COSC stopped reporting a brand-by-brand breakdown (watch nerds are up in arms…).
Here are five chronometers to set your watch – and your life – by.
Rolex Datejust 41
No one knows how many watches Rolex makes a year – no one outside the chocolate factory, that is. The only gauge we ever had was that derived from stats released by COSC, which put Rolex on top of the chronometer pile with around 800,000 movements a year. Rolex’s new generation of movements are notoriously bullet-proof and come with five-year guarantees and 10-year recommended service intervals, the industry lead. One of those is Calibre 3235, which appears in the Datejust 41, seen here in Oystersteel and white gold with a dark rhodium dial and a Jubilee bracelet.
£6,950, shop now
Omega Seamaster Railmaster Co-Axial Master Chronometer 40mm
Omega’s Master Chronometer movements are, no debate, some of the very best series-produced movements on the planet. As well as being COSC-certified, they’ve also been signed off by METAS, a Swiss body that tests watches and movements for accuracy, even when blasted with magnetic fields (Master Chronometers are famously resistant to 15,000 gauss, about the same as emitted by an MRI scanner) and temperature changes. It also guarantees Omega’s claims of power reserve and water resistance. In the case of the Railmaster, one of the brand’s strongest designs, that means 55 hours and 150 metres, respectively.
£3,600, shop now
Breitling Transocean Chronograph
A decade or so ago, Breitling embarked on a massive in-house movement programme. Spearheading it was the Breitling 01, a chronometer-certified chronograph. That wasn’t it’s only quality signifier. Breitling 01 had a 70-hour power reserve, one of the earlier three-day units that are increasingly commonplace these days. It also gave the watch its traditional 3, 6 and 9 dial layout, more often than not the preference of chronograph buffs. Here, it features in Breitling’s jet age-inspired Transocean, a classic steel chronograph with a black dial and a Milanese mesh bracelet.
£6,330, shop now
Oris Artelier Chronometer, Date
There are few brands that can compete with Oris on a watch-to-value ratio basis, and few that offer so much for under £1,500. The Artelier Chronometer, Date does what it says on the tin, its automatic mechanical movement surrounded by a pleasingly fluid 40mm steel case, an Art Deco-ish guilloché dial, gilt hands and hour markers, and a see-through case back.
£1,380, shop now
Britain’s very own Bremont has always been a big fan of chronometer-certified movements – supports the brand’s ‘tested beyond endurance’ mantra and fits with the reliable tool watch billing. The MBII, now a Bremont signature, is one such piece. Produced to give civilians a version of the watch it only makes for pilots who’ve successfully ejected from a plane using a Martin Baker ejector seat, the MBII also features an anti-shock movement mount that – we’re told – protects the movement in the event of an ejection. Happy to go along with that without feeling too strong a need to put the theory to the test…
£3,595, shop now