December 1, 2019

Rewriting History

MB&F set out to improve a classic complication and wound up creating a modern masterpiece with its Legacy Machine Perpetual Calendar.

The perpetual calendar is one of watchmaking’s most fascinating and frustrating complications.

Since it first appeared in a wristwatch nearly a century ago, horological enthusiasts have prized the perpetual calendar’s ability to mimic the Gregorian calendar without needing any manual adjustment during “short months” and leap years. However, that laissez-faire functionality comes with some compromises.

First, most perpetuals have tiny buttons inset on the caseband that are used to change the calendar indications. Those adjustments require a special tool that can accidentally scratch the case if your hand happens to slip while making a change.

Another, more-significant drawback, is the damage you can do internally to the movement. That can happen if you attempt to make an adjustment when the calendar is changing — a process that generally occurs between 9 p.m. and 2 a.m. Doing this can cause major damage that’s expensive to repair.

MB&F founder Maximilian Büsser says: “I call perpetual calendars boomerang watches because they come back for repair so often. The mechanisms jam, block, break, or jump days when they shouldn’t.”

Thankfully for watch enthusiasts, Büsser is not the kind of person to leave well-enough alone. That’s why he began looking for a way to create new kind of perpetual that would allow collectors to have their horological cake and eat it, too.

His search led him back to independent Irish watchmaker Stephen McDonnell, who’d previously helped MB&F develop its first watch, Horological Machine No. 1. When Büsser came calling in 2012, McDonnell happened to have an idea for a movement that would resolve the shortcomings inherent in conventional perpetual calendars. Three years later, in 2015, the first Legacy Machine Perpetual was unveiled.

MB&F Legacy Machine Perpetual white gold

The white gold LM Perpetual is recognizable by its gray baseplate.


The Legacy Machine Perpetual is nothing less than a sweeping reinvention of one of watchmaking’s most-hallowed complications, one that completely rewrites the rule book in terms of functionality and aesthetics.

To avoid building on mistakes from the past, MB&F and McDonnell developed the LM Perpetual’s hand-wound movement from the ground up. The result is a completely integrated, purpose-built caliber, two key distinctions that set it apart from nearly every other perpetual on the market today.

Why is that important? The main reason is that calibers in most perpetuals are constructed a bit like a layer cake with a calendar module stacked on top of a base movement. The calendar indications are synchronized by a long lever that runs across the top of the module and passes through the center. This “big lever” design takes less time and money to manufacture, but it’s prone to the kinds of jamming and jumping that Büsser wanted to eliminate. In contrast, the LM Perpetual’s calendar and base movement are integrated into a single piece. This holistic approach results in a movement that’s much more dependable.

MB&F LM Perpetual movement

The titanium version of the LM Perpetual has a green baseplate and is limited to 50 pieces.


Another disadvantage of the classic big-lever design is that its calendar is based on a 31-day month. That means when a short month ends, the date hand still needs to cycle through the extraneous days. To avoid this in the Legacy Machine Perpetual, McDonnell created a “mechanical processor” that defaults to a 28-day month and then adds extra days as needed. As a result, the date hand always jumps precisely to 1 at the start of a new month instead of fast-forwarding through those extra days.

Another vital benefit of the processor design is peace of mind. As mentioned earlier, you can severely damage a perpetual calendar by trying to adjust it during the date changeover. That’s not possible in the LM Perpetual because the calendar pushers disconnect when the date is changing, thereby eliminating the risk of human error.

One final improvement will appeal to anyone who’s ever been frustrated by the process of setting a conventional perpetual calendar. Instead of the hard-to-use inset buttons found on most perpetuals, MB&F uses four convenient pushers to individually advance displays for the day, date, month and leap year. The latter is especially important because in a typical perpetual, the only way to advance the leap year counter is by cycling through 12 months. This can be particularly vexing when you need to move the leap-year indicator ahead several years.

MB&F Legacy Machine Perpetual back

The LM Perpetual features a fully integrated 581-component caliber.


The Legacy Machine Perpetual’s mechanical innovations certainly improved the experience of owning a perpetual, but they also gave MB&F more latitude for aesthetic expression.

Two changes, in particular, had a profound effect on the look of the watch. First, eliminating the big lever system meant that a traditional dial was no longer necessary, which opened up a clear view of the movement below. Second, the caliber’s integrated design allowed the calendar mechanism to be positioned on top of the main plate, making it — along with the suspended balance wheel and skeletonized subdials — the stars of the show.

McDonnell says, “It’s all about the mechanism. What’s the point in creating something that looks amazing, functions beautifully, and is completely innovative, and then cover it up with a dial? I’ve never understood that about other perpetual calendars.”

An instant sensation, the LM Perpetual resonated immediately with collectors who understood its revolutionary movement and appreciated its symmetric beauty. Three years ago, the watch industry acknowledged MB&F’s achievement when the Grand Prix d’Horlogerie de Genève awarded the Legacy Machine Perpetual its coveted Calendar Watch Prize. Even today, its impact continues to grow as more people discover it. You can experience the Legacy Machine Perpetual for yourself at Cellini.

Click here to view the MB&F collection online at Cellini Jewelers.

MB&F Legacy Machine Perpetual wristshot

The 44mm case includes four pushers to quickly and easily adjust the calendar displays.