The dial of the new Lange 1 Tourbillon Perpetual Calendar is not quite solid. It is made of a semi-transparent sapphire that lets you see through to the mechanics beneath. This is not a skeleton watch in the traditional sense. The view is controlled, architectural, and serves a very specific purpose.
For more than a decade, A. Lange & Söhne has used its “Lumen” series to explore what happens when its rigorously structured watches are designed to be read in the dark. This latest version, housed in a platinum case, applies the concept to two of watchmaking’s most demanding complications, a tourbillon and a perpetual calendar, all within the strict asymmetrical geometry of the Lange 1 family.
The transparency is a functional requirement. The dial needs to let ultraviolet light pass through to energize the luminous compound on the display elements sitting below it. The perpetual calendar’s large peripheral month ring, the outsize date discs, and the moonphase all require a constant charge to glow. The solution was to make the main dial permeable to light.
A New Kind of Transparency
This decision creates an unusual effect. The watch exposes its own construction from the front. You can see the perlage finishing on the mainplate, a texture usually reserved for the view through a caseback. It makes the engineering part of the watch’s daily character. The complex mechanism for the brand’s signature outsize date, with its tens cross and units disc, is made visible as it operates.
The displays themselves are rethought for luminescence. It is the first time the brand has produced a luminous moonphase. The celestial disc behind the moon rotates once every 24 hours, showing a bright, starless sky for day and a dark, star-filled sky for night. The leap-year indication, set in a small aperture at six o’clock, is also coated to glow with the same intensity as the date.
All the calendar displays are engineered to switch instantaneously at midnight. This ensures a clean, unambiguous reading at all times, a detail consistent with the brand’s focus on legibility and precision. The entire calendar, if kept running, will require its first manual correction on March 1, 2100.
Complications in Plain Sight
While the calendar mechanism is revealed, the tourbillon is not. A subtle inscription at 12 o’clock is the only clue to its presence. The complication, complete with a stop-seconds mechanism for precise setting, remains hidden from the dial side. It’s a choice that prioritizes the clean information hierarchy of the Lange 1 layout over the spectacle of the spinning cage.
The newly developed calibre L225.1 drives the watch. Its construction is a direct response to the demands of the dial, integrating the perpetual calendar and tourbillon while accommodating the unique transparent architecture. The result is a watch that feels both familiar in its layout and entirely new in its depth. The light is not just an effect. It is a consequence of how the watch is built.
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