Fantastic Calibers and Where to Find Them: MB&F’s Legacy Machine Perpetual Calendar

One of our favorite modern independent watch brands, MB&F has come a long way from its earliest days. The Horological Machine 1, released in 2006, confused and bewildered collectors and retailers. The Horological Machine 11 Architect from last month’s Dubai Watch Week (Nov. 2023), well the watch community was mesmerized and demand is huge. Avant-garde watchmaking has become something much bigger than an ultra-small niche for a handful of sci-fi enthusiasts. 

With the rise of avant-garde watchmaking, specifically the creations of MB&F, there is tremendous focus on design. Case shape, in particular, often grasps the attention of collectors and has a tendency to overshadow the serious watchmaking that drives equally innovative movements. The architecture principle, “form follows function,” is certainly true with MB&F – there is no innovative design without innovative movements. 

That’s why we’re focusing on one of MB&F’s most significant technical contributions to the history of watchmaking – Stephen McDonnell’s revolution of the perpetual calendar movement found in the Legacy Machine (LM) Perpetual. Beginning a series on the most important movements in modern independent watchmaking, we’re diving into the LM Perpetual and what makes it so special.

Progress – how it works in watchmaking

Any discussion of what makes the Legacy Machine Perpetual’s movement legendary requires first a brief moment on the chaotic nature of progress in watchmaking (or any technical field). 

It’s astoundingly meticulous. Optimizations and evolutionary leaps often appear trivial to the non-practitioner of a given engineering field. There are sometimes years, decades, and centuries between the invention of a mechanism and its next improvement or complete revolution. This constitutes the blindspots that exist in every discipline - the “it’s good enough” or “that’s how it’s always been done” mentality that locks things in place.

Photo of Stephen McDonnel | Credit: MB&F Press Page

True progress, something that brings a watch mechanism to a whole new place, comes with significant uncertainties as well. While the initial ideas are drawn and modeled with CAD, there’s no guarantee that the theory of smooth function will meet the reality of manufacturing and assembly. McDonnell covers the entire prototyping process of the LM Perpetual in an amazing hour-long presentation (The Trials and Tribulations of Watch Innovation) from last year’s Dubai Watch Week. This is one of the most entertaining and easily recommendable presentations for anyone interested in watches. In it, McDonnell mentions that there is a constant “haunting fear” that the whole house of cards for the design of a new movement will come crashing down by some unknown mechanical impasse. It’s something that kept McDonnell awake at night, poked into his dreams while asleep, and took a serious toll on his mental health.

This is not something to aspire to, per se, but it is the reality of most innovation. It begins with an unhappiness with existing conventions, the creative will to find an improved solution inserts itself in the picture, and a nearly (or completely) neurotic anxiety of uncertainties that may cause failure exists throughout. This is the backdrop for one of the most important and technically progressive movements in modern independent watchmaking. 

The trouble of perpetual calendar complications

Traditional perpetual calendars exist with a default 31-day month. For months, like February, the additional days are effectively deleted by jumping through inapplicable dates. In the month of February, perpetual calendars will typically scroll through the 29th, 30th, and 31st to the correct March 1st date. This is done by a grand levier (long lever) system – a lever that runs across the entire center of many perpetual calendar complications and communicates through a mechanical program when dates must be skipped. That mechanical program, similar to a computer program, is operated by specifically designed wheels that are shaped differently for months with 28, 29, and 30 days. Every instance when the grand levier interfaces with a non-31-day wheel, that information is transmitted to all other subdials to ensure the perpetual calendar tracks time in a correct manner.

On one hand, all of this is ingenious. It’s worked for centuries. But, this system is extremely fragile and prone to require service. Max Büsser has publicly stated that MB&F would never make a perpetual calendar timepiece because they are “boomerangs” - they leave the workshop and return quickly for servicing. McDonnell’s complication design for the LM Perpetual shifted Max’s perception. This was something much more robust than any previous grand levier systems. 

The historical leap for perpetual calendars 

The LM Perpetual is a purpose-built caliber, no modules or base movement, that brought a new “mechanical processor” system to the table. This is why the LM Perpetual is a historical movement. 

The mechanical processor utilizes a default 28-day month and adds extra days as required. Every month, there’s always the exact number of required days. This innovative perpetual calendar design utilizes superimposed disks that program each month on the 25th day, adding however many additional days are required past 28. Since this architecture operates without a grand levier, there’s no requirement to skip days in February, April, June, September, and November. This removes one of the major headaches for collectors that leads to frequent servicing on perpetual calendar timepieces – no jumping days when they shouldn’t. 

QP Magazine has a brilliant visual representation of the mechanical processor system complication – worth viewing here for visual reference. 

Two major improvements to perpetual calendar complications that were opened by McDonnell’s mechanical process: 

  1. Without a traditional grand levier system, collectors no longer need to scroll through up to 47 months to set the leap year. The LM Perpetual’s dedicated quickset pusher adjusts the year.

  2. The mechanical processor system has an in-built safety feature that disconnects the quick-set pushers during date changeover. This eliminates another one of the major causes for required servicing on perpetual calendar timepieces – an adjustment is made during the wrong hours of the day. 

While the mechanical processor innovation and all of the caliber’s 581 components are astounding, there’s nothing more impressive than the fact that all these improvements ultimately serve the collector, easy usability, and smooth long-term operation. This isn’t superfluous innovation, or innovation that can only be most appreciated technically by other watchmakers. This is innovation felt by the wearer of the watch in everyday life.

MB&F LM Perpetual Titanium | Credit: MB&F Press Page

On a closing note, the design for McDonnell’s perpetual calendar complication opens new possibilities far beyond robustness and user-friendliness. It creates an entirely new way of dealing with perpetual calendar aesthetics. With the traditional grand levier system, dials needed to be full because that long lever runs through the center and occupies a lot of space. McDonnell and MB&F leveraged this new-found freedom to the maximum by skeletonizing subdials and displaying the perpetual calendar complication through the dial. Here, we can observe things as wild as an extra-long balance staff that enables the separation of the balance, seen on the dial, and the escapement, viewed through the caseback. 

Perfect symmetry, a new conception of the perpetual calendar opened entirely new aesthetic possibilities for one of the most fixed, classically-styled complications in watchmaking. 

Titans in watchmaking, Stephen McDonnell, MB&F, and the LM Perpetual came together to craft one of the most important innovations in the 21st century.

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