Perpetual Moon 41.5 Platinum LTD 28 fern-green

Clear Skies, Captured in Platinum

At the crossroads of astronomical precision and refined Swiss craftsmanship, Arnold & Son unveils the Perpetual Moon 41.5 Platinum—a timepiece that transforms the moon-phase complication into a luminous composition of colour, depth, and celestial poetry.

Housed in a 41.5mm case crafted from Pt950 platinum, this limited edition of 28 pieces brings a distinctive freshness to the Perpetual Moon collection. The pale radiance of platinum, the cool intensity of Fern Green, and the midnight blue of the lunar sky create an original chromatic harmony—one that evokes the quiet brilliance of a moonlit night.

Astronomical Precision: The A&S1512 Calibre

At the heart of the Perpetual Moon 41.5 Platinum beats the Calibre A&S1512, a hand-wound Manufacture movement entirely developed, manufactured, decorated, assembled, adjusted, and cased by Arnold & Son in La Chaux-de-Fonds. Conceived to track the lunar cycle with exceptional accuracy, this calibre reflects the Maison’s deep connection to astronomy and marine chronometry.

Operating at a frequency of 3 Hz and offering a 90-hour power reserve, the A&S1512 calibre combines technical reliability with celestial refinement. On the caseback, a secondary moon-phase indicator allows the display to be adjusted quickly and precisely, reinforcing the watch’s role as both an elegant timepiece and a true astronomical instrument.

A Moon of Mother-of-Pearl

The Perpetual Moon 41.5 Platinum is defined by its large white mother-of-pearl moon, realistically rendered with hand-painted shadows and enhanced with Super-LumiNova. Set against a grained sky with midnight-blue PVD treatment, the moon appears suspended in a deep celestial landscape, revealing a new luminous presence after dark.

The display follows the true duration of a complete lunar cycle: 29 days, 12 hours, 44 minutes, and 2.8 seconds. Thanks to Arnold & Son’s meticulous calculation, the moon phase would require only a one-day correction after 122 years, provided the watch remains regularly wound.

A Fern Green Dial: Shimmer, Depth and Constellations

The identity of the Perpetual Moon 41.5 Platinum is expressed through its Fern Green dial, animated by Arnold & Son’s “Stellar Rays” decor. Irregular engraved rays of varying depths and widths create a sophisticated shimmer, while layers of transparent lacquer accentuate the play of light and bring depth to the composition.

Around the moon, the Big Dipper and Cassiopeia constellations are hand-painted and coated with luminescent material. Chosen as references to John Arnold’s history as a maker of naval chronometers, these guiding stars recall the celestial points that have helped navigators orient themselves since time immemorial.