Typically complex and easily broken, the perpetual calendar has been made foolproof with the new MB&F Legacy Machine Perpetual. Developed by Irish watchmaker Stephen McDonnell, the Legacy Machine Perpetual accomplishes that by rethinking the traditional calendar mechanism both technically and visually, resulting in a watch easily adjusted via pushers and featuring a skeletonised dial that reveals the intricate workings of the calendar.

An Irish idea

Ordinary perpetual calendar mechanisms have gears set up for a 31-day month. For months with less than 31 days, the mechanism quickly cycles past the extra days (29, 30 and 31) to arrive at the 1st of the following month. This is powered by gears, levers and springs, with one large date lever that triggers the other indications.

Stephen McDonnell, however, had other ideas. An Irish watchmaker who was formerly an instructor at Swiss watchmaking academy WOSTEP (short for “Watchmakers of Switzerland Training and Educational Program”), McDonnell was instrumental in getting MB&F off the ground when it was established. He helped assemble and finish the brand’s first wristwatch, the HM1, after it ran into delays with its movement supplier.

McDonnell’s construction relies on a 28-day month, with gearing to account for extra days when necessary. A stack of gears, with each to trigger one calendar indication, is the heart of the perpetual calendar. Because it has a smaller footprint than a traditional lever-based mechanism, the entire calendar mechanism can be open-worked and visible on the dial.

While the construction of the calendar makes it more robust, it also has a built-in safety function that disengages the buttons on the case when the date is changing across midnight. Pressing the buttons during the date change has no effect, preventing any damage to the movement. Besides the easy to access buttons on the case – they are raised so no stylus is needed – the Legacy Machine Perpetual also has a leap year indicator that can be set directly. That differs from traditional calendars that require advancing the month to change the leap year.

Simple yet complicated

Despite being simpler to use, the Legacy Machine Perpetual movement is more complex in construction, comprised of some 581 parts. That’s more than the 475-component count of the movement inside the HM6 tourbillon, and in fact more than any other MB&F movement to date. In contrast, a typical perpetual calendar movement, like the Patek Philippe calibre 240 Q for example, is made up of 250 or so components.

Though the complication is the first of its kind for MB&F, the aesthetic follows that established by the earlier watches in the Legacy Machine series, namely the LM1 and LM2. Towering over the calendar is an enormous balance wheel, the signature feature of the Legacy Machine series. Beating at a languid 18,000 beats per hour, it’s held aloft by a large, arched bridge made of steel that’s been rounded and polished.

The balance wheel in turn is connected to the escapement on the back of the back via an exceptionally long balance staff that’s almost as long as the watch is high. Because the balance sits so high, the crystal on the front is high and domed to accommodate.

The movement is impressively decorated, with carefully shaped bridges with inward corners that bespeak of a high level of hand-finishing. Wide polished bevels with sharply defined lines frame all of the bridges, which have surfaces covered in strongly defined Geneva stripes. Even the pallet fork is polished on its face and bevelled on its edges, illustrating a degree of finish that’s the best yet found on an MB&F. The result is reminiscent of Laurent Ferrier movements, most probably finished with similar techniques.

The escape wheel at centre and the pallet fork with its twin jewels to its left

The black polished click spring for the barrel ratchet

Notice the diamond-cut countersinks for the screws

Specs and price

The Legacy Machine Perpetual is substantially sized, with a 44mm case that’s 17.5mm high. It’s a limited edition of 25 pieces each in red gold and platinum, priced at SFr138,000 and SFr168,000 respectively.

That puts the Legacy Machine Perpetual amongst the priciest perpetual calendar watches on the market, though it is also amongst the most complicated and finely finished. Future editions of the Legacy Machine Perpetual will be introduced in subsequent years in different case materials.

Parmigiani Fleurier recently introduced one of the thinnest tourbillons ever, equipped with an in-house movement just 3.4mm high, with the Tonda 1950 Tourbillon, 

A vertically integrated watchmaker that makes its own dials and movements, Parmigiani Fleurier recently introduced the calibre PF517, the one of the slimmest self-winding tourbillon movement on the market. It’s found inside the Tonda 1950 Tourbillon, a watch as uncluttered as the movement is thin. At 40.2mm in diameter the case is not yet, but feels larger than it is, due to the thinness of the case, narrow bezel and plain dial. The dial is unadorned, with almost nothing superfluous except for lettering around the aperture for the tourbillon. Because the dial is so clean, the eye is immediately drawn to the tourbillon. 

As expected for a movement this thin, the tourbillon is of the flying variety, instead of the more traditional sort with a bridge that requires more height. Another reason for its slimmest is the minimalist tourbillon cage that’s made of titanium and weighs just 0.255g, making it the lightest ever. Beyond the height reduction, a lighter tourbillon cage should improve timekeeping since it requires less energy to rotate, meaning more energy can be used to keep the balance wheel oscillating. The movement in the Tonda 1950 Tourbillon is based on the PF700 calibre found in the Parmigiani Tonda 1950, and also the Slim d’Hermes (which won the recent Grand Prix d’Horlogerie de Geneva). That’s the reason the tourbillon regulator is positioned at the unusual seven o’clock position, because in the base movement the balance wheel is in the same place (though Parmigiani tenuously explains the 7:08 placement as the time of Michel Parmigiani’s birth in the year 1950). 

Typical of Parmigiani movements the calibre is elegantly designed and constructed, with a platinum micro-rotor to help keep it thin. The finishing is also of a high standard, clean and nearly executed, though not quite as elaborate as the far more expensive tourbillons Parmigiani unveiled at SIHH 2015. The Tonda 1950 is after all the entry-level tourbillon wristwatch from Parmigiani, priced about a quarter less than the next most expensive model.

The Tonda 1950 Tourbillon is 8.65mm high in its entirety, thin enough that it’s bested only by one watch, the Breguet Tourbillon Extra-Plat 5377 that’s 7mm thick. But it’s not the thinnest automatic tourbillon ever, that distinction goes to the 4.8mm high Audemars Piguet tourbillon of 1986 that managed to be so thin only because the movement was built onto the case back of the watch. And it was also thin enough to be less than reliable.

The Tonda 1950 Tourbillon is starts at US$130,000 or S$214,000 for the basic model in gold, fancier versions with semiprecious stone dials or diamond setting costs more.  Correction November 3, 2015: The Tonda 1950 Tourbillon is not the thinnest self-winding tourbillon, that title goes to the Breguet reference 5377.