IWC SCHAFFHAUSEN Portugieser Eternal Calendar presented at Watches and Wonders 2024.

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IWC SCHAFFHAUSEN Portugieser Eternal Calendar with Moon Phase accuracy of 45 Million Years. The watch is based on the same design as the existing perpetual calendar. All its displays can be advanced using the crown. However, while the perpetual calendar is programmed for a four-year cycle, the Portugieser Eternal Calendar features an additional mechanism. Every four years at the end of February, a new module informs the calendar about whether the leap year takes place or not. This so-called 400-years gear completes only one revolution every four centuries. It contains three indentations, which cause the calendar to skip three leap years over that period. This module is designed with impressive efficiency and technical elegance and consists of only eight parts, underscoring IWC Schaffhausen’s engineering approach to fine watchmaking.

While the Da Vinci Perpetual Calendar Chronograph (Ref. IW3750) from 1985 featured a moon phase precision of 122 years, the first Portugieser Perpetual Calendar (Ref. IW5021) from 2003 impressed with a moon phase accuracy of 577.5 years. IWC’s engineers have now taken on the challenge to develop a new moon phase display with unprecedented precision.

The difficulty in displaying the moon phase on the dial of a watch lies in the fact that the moon does not follow a daily rhythm in its orbit around the Earth. A cycle from new moon to new moon – one lunation – does not last 30 days, but rather 29 days, 12 hours, 44 minutes, and 2.88 seconds. The duration of one calendar month must therefore be reduced as close as possible to one lunar cycle. This is achieved by placing a reduction gear between the base movement and the moon phase disc. The key to high precision lies in the quantity of wheels used, their proportions and the number of teeth they have. IWC’s engineers have now used a special computer program to simulate more than 22 trillion different combinations. For the Portugieser Eternal Calendar, they came up with a new reduction gear train using three intermediate wheels. Mathematically, the display will only deviate from the moon’s orbit by one day after 45 million years. Another challenge consisted in integrating this new gear train into the confined space of the eternal calendar module.

The moon phase is displayed on the dial using the characteristic Double MoonTM indication, which shows the moon as seen from the Northern and Southern hemispheres. The display consists of two super- imposed discs. A celestial disc with two small circular openings rotates above an immobile lower disc with two dots. This negative representation gives the impression that two small moons are waxing or waning. Here, the lower disc is made of titanium and decorated with a Guilloché pattern. The upper disc is made of glass.

The Portugieser Eternal Calendar features an intricately finished platinum case with polished and brushed surfaces. Another highlight is the glass dial, which is manufactured in a complex process. In the first step, the underside of the dial is frosted and lacquered in white. The subdials are machined and polished separately and subsequently fixed onto the dial. In the next step, the printing is applied, and the appliques are mounted by hand. The depth of the glass lends the print and appliques a floaty lightness. The numerals and the characteristic Portugieser minute scale are printed on a white lacquered flange sitting between the glass dial and the front glass. The box-glass sapphire crystals are machined and polished in an elaborate process. The Portugieser Eternal Calendar is fitted with a black alligator leather strap from the Italian leather artisan Santoni with a platinum folding clasp.

At work inside the platinum case is the newly developed IWC-manufactured 52640 calibre. The high-end calibre features a highly efficient Pellaton winding system. Using movements of the rotor in both directions, it reliably builds up a power reserve of seven days (168 hours) in the two barrels. Parts of the winding system that are subject to extremely high stresses are manufactured using virtually wear-free zirconium oxide ceramic. The movement has been elaborately finished with circular graining and Geneva stripes and can be admired through the box-shaped sapphire glass case back.

REF. IW505701
FEATURES
Mechanical movement – Pellaton automatic winding system – Power reserve display –
Secular perpetual calendar with displays for the date, day, month, year in four digits –
Perpetual moon phase with 45,000,000 years accuracy for both northern and southern hemispheres – 400-years gear for the recognition of irregular leap years – Small hacking seconds – Rotor in 18-carat gold – See-through sapphire glass back

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