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Reinventing the perpetual calendar

First launched in 2015, the LM Perpetual has been crafted since in red gold, platinum, white gold and titanium. A new 18k yellow gold case with striking blue face now joins the series: a limited edition of 25 pieces.

Beginning with a blank sheet of paper, MB&F and independent Irish watchmaker Stephen McDonnell have completely reinvented that most traditional of horological complications: the perpetual calendar. The result is Legacy Machine Perpetual, featuring a visually stunning in-house movement – developed from the ground up to eliminate the drawbacks of conventional perpetual calendars.

The fact that the new complication looks sensational and can be fully appreciated dial-side is just one of the many benefits offered by the new movement, controlled by a mechanical processor (patent pending).

LM Perpetual features a fully integrated 581-component calibre − no module, no base movement − with a revolutionary new system for calculating the number of days in each month. And it holistically reinterprets the aesthetics of the perpetual calendar by placing the full complication on dial-free display underneath a spectacular suspended balance.

The perpetual calendar is one of the great traditional complications, calculating the apparently random complexity of the varying numbers of days in each month − including the 29 days in February during leap years. But traditional perpetual calendars do have a few drawbacks: dates can skip; they are relatively easy to damage if adjusted while the date is changing; and the complications are usually compromises of modules powered by base movements.

The fully integrated, purpose-built movement of Legacy Machine Perpetual has been designed from scratch for trouble-free use: no more skipping dates or jamming gears, and the adjuster pushers automatically deactivate when the calendar changes, so no problems there either!

Traditional perpetual calendar mechanisms use a 31-day month as the default and basically “delete” superfluous dates for the months with fewer days – by fast-forwarding through the redundant dates during changeover. A traditional perpetual calendar changing from February 28 to March 1 scrolls quickly through the 29th, 30th and 31st to arrive at the 1st.

LM Perpetual turns the traditional perpetual calendar system on its head by using a “mechanical processor” instead of the conventional space-consuming grand levier (big lever) system architecture. The mechanical processor utilises a default 28-day month and adds extra days as required. This means that each month always has the exact number of days required; there is no fast-forwarding or skipping redundant days. And while the leap year can only be set on traditional perpetual calendars by scrolling through up to 47 months, LM Perpetual has a dedicated quickset pusher to adjust the year.

With its open dial revealing the full complication and suspended balance, it’s the harmonious mechanical beauty of LM Perpetual that really steals the show. And in an interesting technical twist, that eye-catching balance hovering on high is connected to the escapement on the back of the movement by what is likely to be the world’s longest balance staff.

Using an innovative system developed especially for Legacy Machine Perpetual, the subdials appear to “float” above the movement with no visible attachments. The skeletonised subdials rest on hidden studs, which is technically impossible with traditional perpetual calendar mechanisms because they would block the movement of the grand levier.

Taking a clockwise tour of the dial, at 12 o’clock we see the hours and minutes nestled between the elegant arches of the balance; day of the week at 3 o’clock, power reserve indicator at 4 o’clock, month at 6 o’clock, retrograde leap year indicator at 7 o’clock, and date at 9 o’clock.

The Legacy Machine Perpetual won the Best Calendar Watch Prize at the GPHG (Grand Prix d’Horlogerie de Genève) in 2016.

Legacy Machine Perpetual technical details

Legacy Machine Perpetual is available:

– in platinum 950 with blue face (limited to 25 pieces);

– in 18k red gold with grey face (limited to 25 pieces);

– in 18k white gold with purple face (limited to 25 pieces);

– in 18k white gold with dark grey face;

– in grade 5 titanium with green face (limited to 50 pieces);

– and now in 18k yellow gold with blue face (limited to 25 pieces)

‘Friends’ responsible for LM Perpetual

Concept: Maximilian Büsser / MB&F

Product design: Eric Giroud / Through the Looking Glass

Technical and production management: Serge Kriknoff / MB&F

Movement design and finish specifications: Stephen McDonnell and MB&F

Movement development: Stephen McDonnell and MB&F

R&D: Ruben Martinez, Simon Brette and Thomas Lorenzato / MB&F

Wheels, pinions, movement, axis component: Paul-André Tendon / Bandi, Daniel Gumy / Decobar, Le Temps Retrouvé and Swiss Manufacturing 

Balance wheel bridge and plates: Benjamin Signoud / AMECAP

Balance wheel: Andréas Kurt / Precision Engineering 

Balance spring: Stefan Schwab / Schwab-Feller 

Bridges: Rodrigue Baume / HorloFab

Perpetual calendar parts: Alain Pellet / Elefil 

Hand-engraving of movement: Glypto and Eddy Jaquet

Hand-finishing of movement components: Jacques-Adrien Rochat and Denis Garcia / C-L Rochat

PVD-treatment: Pierre-Albert Steinmann / Positive Coating 

Movement assemblage: Didier Dumas, Georges Veisy, Anne Guiter, Emmanuel Maitre, and Henri Porteboeuf / MB&F

In-house machining: Alain Lemarchand and Jean-Baptiste Prétot / MB&F

Quality Control: Cyril Fallet / MB&F

Case: Alain Lemarchand and Jean-Baptiste Prétot / MB&F

Gold ingots CoC ( Chain of Custody) : Nathalie Guilbaud / Cendres et Métaux

Case decoration : Bripoli

Dial: Hassan Chaïba and Virginie Duval / Les Ateliers d’Hermès Horloger

Buckle: G&F Chatelain and Nathalie Guilbaud / Cendres et Métaux

Crown and correctors: Cheval Frères 

Hands: Isabelle Chillier / Fiedler

Sapphire crystals: Martin Stettler / Stettler

Technical Specifications - LM Perpetual Calendar Yellow Gold

Case:   Hours, minutes, day, date, month, retrograde leap year and power reserve indicators Case Material: 18k 5N+ red gold, 18k white gold, 18k 3N yellow gold, platinum 950, grade 5 titanium. Dimensions: 44 mm x 17.5 mm Number of components: 69 components Water resistance: 30 m / 90' / 3 atm Sapphire crystals Sapphire crystals on top and display back treated with anti-reflective coating on both faces

Movement:   Fully integrated perpetual calendar developed for MB&F by Stephen McDonnell, featuring dial-side complication and mechanical processor system architecture with inbuilt safety mechanism. Manual winding with double mainspring barrels. Bespoke 14 mm balance wheel with traditional regulating screws visible on top of the movement. Superlative hand finishing throughout respecting 19th century style; internal bevel angles highlighting hand craft; polished bevels; Geneva waves; hand-made engravings. Power reserve: 72 hours Balance frequency: 18,000bph / 2.5Hz Number of components: 581 Number of jewels: 41

Strap:   Black, grey, brown or blue hand-stitched alligator strap with gold / platinum / titanium folding buckle matching case material.


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