The calibre L901.5
SEEN THROUGH A WATCHMAKER’S LOUPE (2 MB)

MOON PHASES TRANSFORMED INTO ENGINEERING.

The complexity of this movement is due not only to the numerous functions it accommodates, but also to the strict requirements imposed on its accuracy. One of the truly intriguing challenges was the calculation of the transmission ratio for the four-wheel train that drives the moon-phase display with an accuracy of 99.998 percent in relation to the true synodic orbit of the earth's satellite. Since the mechanism is coupled to the continuum of the hour wheel, the display is always in motion, just like the real moon. The integration of the twin-disc mechanism for the outsize date and of the mechanism used to display the power reserve was also a daunting task.

The calibre L901.5

A COMPLEX MOVEMENT MADE OF 398 PARTS.

The three-quarter plate made of untreated German silver affords a solid footing for each of the 398 parts that interact in this timepiece. The plate is decorated with Glashütte ribbing. A total of 54 synthetic ruby jewel bearings accent the movement and minimise mechanical friction. Nine of them are set in precious gold chatons which are secured to the three-quarter plate with blued screws.


THE QUEST FOR MECHANICAL PERFECTION.

The shock-proofed screw balance with its Nivarox-1 balance spring executes 21,600 semi-oscillations per hour and is adjusted in
five positions. The manually engraved balance cock carries the whiplash precision index adjuster. This patented adjustment system makes it possible to accurately set the impulse pin relative to the pallet fork without removing the balance wheel - a detail greatly appreciated by watchmakers in charge of customer service.