Ferdinand Berthoud Chronomètre FB 2RE

The Ferdinand Berthoud Chronomètre FB 2RE stands out as one of the most remarkable watches of 2020. Indeed, it won the coveted Chronometry Prize at GPHG 2020. Mark McArthur-Christie provides his own light-hearted take on this exceptional creation.

Mel Nichols, a former editor of CAR magazine, tells a story about the Mercedes 450SEL 6.9 and the great Argentinian racing driver Fangio. Here’s one version of it, recounted on the Pistonheads forum:

“At the old SMMT Test Day at Silverstone in 1975 or 1976, Mercedes brought a LHD 6.9 with Fangio to drive it. LJKS (LJK Setright) and I jumped in with him. Leonard sat in the front with Juan Manuel, I was in the back right side and someone else I can’t remember in the left rear seat.

“Fangio took us around the Grand Prix circuit flat out, beautifully, smoothly and uneventfully. We didn’t appreciate quite how fast we were going until, approaching the old, fearsome, mega-fast Woodcote corner Fangio pulled to the left to overtake a racing Pantera that was being shaken down. It was flat out, on the racing line. Its driver was working away at the wheel as it twitched and hopped around through the corner.

“Fangio, driving with one hand, making just tiny movements at the wheel and talking to Leonard all the while, slipped up alongside the Pantera and eased past him. I looked out the side window and grinned at the Pantera driver as we were alongside, just a couple of feet away. I’ll never forget the stunned look on his face as he realised he was being overtaken, in the middle of one of racing’s most challenging corners, by a Mercedes saloon with four people on board. It was too much for him. He backed off and just trundled around slowly until we did a couple more laps and pulled off the circuit. I wonder if he ever knew it was Fangio behind the 6.9’s wheel.”

The 450SEL is, perhaps, the ultimate Q car. It looks elegant enough to pass muster anywhere and only the cognoscenti know what’s under the bonnet. But the key to the 450SEL was torque – a stonking 405 lb ft of it.

Ferdinand Berthoud Chronomètre FB 2RE

There are similarities with Ferdinand Berthoud’s Chronomètre FB 2RE. From the front and at a glance, the 2RE looks simple, deceptively plain and classically-designed. You’d notice it, but probably not cross the street to take a proper look. From the back, though, the horological equivalent of a dry-sumped, 6.9 V8 is obvious – and it’s full-on Haute Horlogerie. But once you understand how the movement and its power management system works, it proves even more remarkable. The 2RE is also all about torque.

Ferdinand Berthoud Chronomètre FB 2RE

On that classical face, the keyword is ‘chronometre’. This watch is entirely devoted to grabbing accurate time by the scruff of its neck and wrestling it to the atelier floor.  Ferdinand Berthoud is leaving nothing to chance here. It has managed to fill the 2RE’s case with a combination of a stopworks on the main barrel to manage its power delivery, a fusée and a remontoire d’égalité. Between them, these three devices make sure that the mainspring’s power is delivered as consistently as possible to the escapement.

But let’s work from the outside in, starting with the round case. Ferdinand Berthoud is best known for making octagonal watches, so this departure in shape isn’t just a whim. In fact, it links back to a cylindrical-cased marine chronometer the original Monsieur Berthoud made in the 1760s known as Marine Clock No.6. This was the clock that won Berthoud the title of “Clockmaker and Mechanic by appointment to the French King and Navy” – the king being Louis XV – and a royal commission to build 20 more marine clocks for the French navy.

It’s not just the case shape, though; there’s a very clear visual link between No. 6’s dial and Ferdinand Berthoud’s Chronomètre FB 2RE. Both are enamelled, although there’s nothing terribly unusual about that. What is unusual is the way the new watch references No. 6’s dial with its use of Roman numerals for the hours and Arabic numerals for the cambered – or bombé – minute track. That’s the kind of work that brings enamellers out in cold sweats; trying to get a consistent depth of grand feu enamel on a surface despite multiple firings. One wonders how many attempts it takes to produce a finished dial. Ferdinand Berthoud says this has never been done on a wristwatch before, and one can see why.

Ferdinand Berthoud Chronomètre FB 2RE

There’s a further echo of No.6 on the side of the 44mm case. See that tiny little window – a hublot or porthole – where you can see the fusée? You’ll find another cut into the cylindrical case side of the original chronometer.

Ferdinand Berthoud Chronomètre FB 2RE

Where the dial is ostensibly simple, classical and restrained, the movement is most definitely not.  That’s not to say it has, in any sense, ditched form for function. The three circles of the main barrel, fusée and balance are in proportion above the remontoire at 6 o’clock. The plate on which they’re mounted is frosted (more on that later) and every component that could carry anglage or spéculaire finishing does. It also hides the going train, allowing the movement’s power components to, quite literally, shine. It’s the sort of movement that you could happily sit and look at even when it’s not running.

That frosting on the nickel silver main bridge… it’s an old technique that’s entirely done by hand with a metal brush. And it takes hours. You take the plate and then use the brush to stipple the surface, with each stroke lifting the metal’s surface slightly so it keeps its shine.

So far, so gorgeous. But the whole point of any watch movement is to get power from the mainspring to the balance as evenly as possible. The variations caused by torque falling off as the mainspring unwinds, tiny variances in friction through the gear train and position, are all enemies of consistent timekeeping. Modern mainsprings are far better at delivering consistent power than their old steel spring ancestors, but those torque variations are still there – and this is a watch that’s all about consistent accuracy.

Ferdinand Berthoud makes sure they’re managing both the start and the end of the powertrain.  At the start, the fusée equalises the mainspring’s torque as it unwinds and, at the end, there’s a remontoire d’égalité that feeds the balance with just the right amount of power on each impulse.

The fusée works a little like the derailleur gears on a bicycle; it compensates for the way the mainspring’s torque falls off as it uncoils within the barrel. The barrel containing the mainspring is linked to a fusée cone that looks like the rear cog-block you see on a bike’s back wheel. Wind the mainspring and the fusée chain coils around the cone.  As the mainspring unwinds, the fusée chain moves on the cone to a different ‘gear’ to equalise the power, a little like a rider shifting down as she goes uphill.

A bicycle chain is simple enough in principle, but the fusée chain inside the Ferdinand Berthoud’s Chronomètre FB 2RE is made from nearly 800 parts, takes a day to put together and is only about as long as a couple of iPhones laid end-to-end. Despite being incredibly thin, it copes with the mainspring’s 3Kg of force quite happily.


Ferdinand Berthoud’s watchmakers weren’t leaving anything to chance – or even just the fusée – they also added a stopwork to the top of the mainspring barrel, using a Maltese cross cam that lets only 60% of the mainspring’s most consistent torque into the movement. The mainspring has enough power to turn the barrel eight times, but the six teeth on the cam reduce it to six revolutions. This way the movement doesn’t get too much energy (at the beginning of the power reserve when the torque is greatest) or too little (at the end of the power reserve when it’s dropped off).

But why stop at just two devices to make sure your mechanical chronometer, using watchmaking techniques developed in the Age of Enlightenment, keeps modern quartz watches awake at night, worrying they’re not just utilitarian but not quite accurate enough?

At this point, Ferdinand Berthoud’s team bring out the big gun – their remontoire d’égalité. This is like a separate power supply that distributes power in precise one-second pulses to the balance.  It sits on its own bridge just at the base of the old-school 2.5Hz, free-sprung balance. On one side of the watch is the stop anchor or lock fork and on the other side sits the remontoire’s own hairspring and a hand-shaped triangular ruby cam. Using ruby rather than metal means two constant issues in watchmaking – lubrication and wear – are removed. The remontoire means the 2RE’s second hand ticks in accurate, single second pulses. Ironically, just like a quartz.

The two-spoke variable-inertia balance itself is designed to be aerodynamic and has four inboard screws for adjustment. It’s large enough to retain inertia and stay stable and it ticks at 18,000 vibrations per hour (2.5Hz), so it reduces its demand on the mainspring’s power reserve.

Ferdinand Berthoud Chronomètre FB 2RE

It gives you some idea of the levels of obsession at Ferdinand Berthoud that the central dead-beat second hand is a different material from the minute and hour hands. They’re gold, but the second hand is titanium. Why? Because remontoires are power-hungry, so this second hand weighing just 0.01g, uses less energy. Oh, and it’s matt-finished so it’s easier to see.

Ferdinand Berthoud Chronomètre FB 2RE

So far, so obsessional. But how accurate is the FB 2RE? Its torque management systems ace COSC tests with the same ease Fangio’s 450 SEL dispatched that Pantera, but that’s not enough for Berthoud’s watchmakers. They submitted the Ferdinand Berthoud Chronomètre FB 2RE to the Fleuritest, conducted by the Fleurier Quality Foundation.

Where COSC is a useful assessment of accuracy in the lab, the Fleuritest measures watches in virtually real-world conditions. One wears a watch, so it makes sense to use a test that reflects the way one moves and rests and, crucially, uses a cased movement running throughout its power reserve period. It seems fitting to let Berthoud’s own watchmakers tell the story:

Ferdinand Berthoud Chronomètre FB 2RE

“The results are beyond dispute: over the entire duration of the power reserve, the readings taken show discrepancies of less than 0.5 seconds on average from the benchmark GPS clock optical measurement. For the FB 2RE model, there is thus very little difference in running time between the first and the last minute – in tests performed in actual conditions, simulating the movements of a watch on the wrist.”

Ferdinand Berthoud Chronomètre FB 2RE


In other words, the Ferdinand Berthoud Chronomètre FB 2RE is just about as consistently accurate as we can currently make a mechanical watch. And, just like its marine chronometer ancestors, it does it in a way that’s profoundly unshouty with a level of underbonnet engineering that’s properly boggling.

Ferdinand Berthoud Chronomètre FB 2RE

Berthoud himself would have been proud.

Further reading

Technical specifications

  • Model: Ferdinand Berthoud Chronomètre FB 2RE
  • Case: 18-carat gold (white or rose); diameter 44 mm; height 14.3mm; water resistance 3ATM (30m); sapphire crystal to the front and exhibition case back.
  • Functions: Hours, minutes, deadbeat seconds, power reserve on the back of the movement, time-setting with stop-seconds device on the balance
  • Movement: Calibre FB-RE.FC; mechanical movement with manual winding, constant force with fusee-and-chain transmission and remontoir d’égalité; frequency 18,000 VpH (2.5Hz); 58 jewels; power reserve = 50 hours
  • Strap: Hand-sewn leather strap with 18-carat rose gold pin buckle
  • Price CHF 210,000 (RRP as at 18.8.2020)
  • Limited Edition: 10 pieces in 18-carat rose gold and a further 10 pieces in 18-carat white gold

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