IWC - Portugieser Eternal Calendar – White – IW505701 – 2025

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Location: United States

Year: 2025

Reference number: IW505701

Accessories: Original Box and Papers

Condition: Excellent

Material: Platinum

Color Dial: White

The IWC Portugieser Eternal Calendar reference IW505701 represents one of the most technically advanced calendar watches ever produced by IWC Schaffhausen. Introduced in 2024 and presented here as a 2025 example, it houses IWC’s first secular perpetual calendar within a 44.4mm platinum case. Its white glass dial, slender appliqués and railway-track minute scale preserve the clean visual language of the Portugieser despite the complexity of its calendar displays.

A conventional perpetual calendar assumes that every year divisible by four is a leap year and therefore requires manual correction in secular years such as 2100, 2200 and 2300. The Eternal Calendar solves this limitation with a newly developed 400-year gear. Completing one rotation every four centuries, the mechanism automatically skips three leap years and accounts for the Gregorian calendar’s exception rules. Provided the watch remains running, its calendar is mechanically programmed to remain accurate through the year 3999.

The dial displays the date, day, month, four-digit year, power reserve and moon phase. IWC’s Double Moon indication depicts the moon as viewed from both the Northern and Southern Hemispheres. Its specially calculated reduction gear was developed after analyzing more than 22 trillion gear combinations and will theoretically deviate from the moon’s actual orbit by only one day after 45 million years.

Powering the watch is the automatic IWC manufacture calibre 52640. Its Pellaton winding system builds approximately seven days of power reserve across two mainspring barrels. All calendar displays are synchronized and can be advanced together through the crown, preserving the intuitive operating system developed for IWC’s earlier perpetual calendars. The movement is visible through the sapphire caseback, revealing its decorated bridges and rotor with an 18-carat gold medallion.

The Portugieser Eternal Calendar received the Aiguille d’Or at the 2024 Grand Prix d’Horlogerie de Genève, the competition’s highest distinction. It was also recognized by Guinness World Records for the extraordinary calculated precision of its moon-phase display.

Specifications

• Brand: IWC Schaffhausen
• Collection: Portugieser
• Model: Eternal Calendar
• Reference: IW505701
• Year: 2025
• Introduced: 2024
• Case: Platinum
• Case Diameter: 44.4mm
• Case Thickness: 14.9mm
• Dial: White glass
• Crystal: Double box-glass sapphire with anti-reflective coating on both sides
• Caseback: Sapphire exhibition caseback
• Movement: IWC manufacture calibre 52640
• Winding: Mechanical and self-winding
• Winding System: Pellaton automatic winding
• Power Reserve: Approximately 168 hours or seven days
• Frequency: 28,800 vibrations per hour
• Jewels: 54
• Components: 396
• Rotor: Decorated rotor with an 18-carat gold medallion
• Calendar Type: Secular perpetual calendar
• Calendar Programming: Accounts for Gregorian leap-year exceptions through the year 3999
• Moon Phase: Double Moon display for the Northern and Southern Hemispheres
• Moon-Phase Accuracy: Theoretical deviation of one day after approximately 45 million years
• Water Resistance: 50 meters
• Strap: Black Santoni alligator leather
• Strap Width: 22mm
• Functions: Hours, minutes, small hacking seconds, date, day, month, four-digit year, power-reserve indication and eternal moon phase
• Special Features: Eight-part 400-year calendar module, crown-controlled synchronized calendar, twin mainspring barrels and double-sided moon-phase display
• Award: 2024 GPHG Aiguille d’Or