The LM Perpetual was first introduced in 2015 and has since been made in a variety of metals, including red gold, platinum, white gold, titanium, yellow gold, and palladium. The LM Eternal Stainless Steel, with its luxurious salmon-coloured plate, will be joined by a new variant in the year 2023. For MB&F, combining steel and fish is an innovative step forward. Ergonomic improvements made to the corrector pushers on the LM Perpetual EVO versions have been carried over to this new release.

MB&F and independent Irish watchmaker Stephen McDonnell started from scratch to make a new version of the perpetual clock, which is the most complicated watch ever made. The result is the beautiful in-house movement in the Legacy Machine Perpetual, which was made from the ground up to fix problems with traditional perpetual calendars.

One of the many benefits of the new mechanically-driven movement is that the new complication looks spectacular and is entirely visible from the dial side.

The LM Perpetual has a completely integrated 581-part calibre and a completely new way to count the number of days in each month. It doesn't have a module or a base movement. Also, the whole look of the perpetual calendar is rethought thanks to a dial-less display that shows all of its complexity below a show-stopping suspended balance.

One of the most complicated things in history is the perpetual calendar, which has to deal with the fact that each month has a different number of days (including 29 days in February during leap years). There are, however, some drawbacks to the conventional perpetual calendar, such as the fact that days can skip, the fact that it is easy to damage if changed while the date is changing, and the fact that the complications are typically compromises of modules powered by base movements.

No more skipped dates, jammed gears, or broken adjuster pushers thanks to Legacy Machine Perpetual's custom-built, integrated movement, which is also programmed to disable when the calendar year advances.

For months with less than 31 days, traditional perpetual calendars "delete" the days that aren't used by skipping them when the month changes. When the date is changed on a traditional perpetual calendar from February 28 to March 1, the dates February 29, 30, and 31 are skimmed over rapidly before the new month begins.

LM Perpetual inverts the conventional perpetual calendar system by employing a "mechanical processor" in place of the cumbersome grand levier (big lever) system design. The month is always set to 28 days, but the mechanical engine can add or remove days as needed. This ensures that there are always exactly the right number of days in a given month, without any months being truncated or having days added that aren't actually needed. Unlike conventional perpetual calendars, which require flipping through up to 47 months to find the leap year, LM Perpetual's quickset button makes it easy to make the necessary leap year adjustments.

The harmonious mechanical beauty of the LM Perpetual is on full display thanks to the open bezel exposing the entire complication and suspended balance. That striking balance up there is linked to the escapement at the rear of the movement by what is almost certainly the longest balance staff in the history of the world.

A special method made for Legacy Machine Perpetual makes it look like the subdials "float" above the movement. In conventional perpetual calendar mechanisms, the grand levier would be impeded by the skeletonized subdials resting on concealed studs.

The hours and minutes are shown at 12 o'clock, between the graceful arches of the balance. The day of the week is shown at 3 o'clock, the power reserve indicator is shown at 4 o'clock, the month is shown at 6 o'clock, the retrograde leap year indicator is shown at 7 o'clock, and the date is shown at 9 o'clock.

In 2016, the Legacy Machine Perpetual triumphed in the Best Calendar Watch category at the GPHG (Grand Prix d'Horlogerie de Genève).

Retail price of the LM Perpetual Stainless Steel is CHF 164,000 + VAT (USD 180,000 / EUR 172,000 + VAT).

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