A paragon of visual balance and legibility, the perpetual calendar model bearing Reference 5320 was designed in 2017 in a white gold case with a cream-lacquered dial. Its vintage style is reinterpreted in a new white gold version fitted with a gilded opaline rose gold dial. The calendar displays are arranged in the characteristic manner of Patek Philippe perpetual calendar watches since 1941, with a twin in-line day/month aperture at 12 o’clock and a date indicated by a hand surrounding a moon-phase aperture at 6 o’clock. These are complemented by two round apertures: one for the day/night indication between 7 and 8 o’clock; and the other for the leap-year cycle between 4 and 5 o’clock — both of which are useful to adjust the calendar. The extremely accurate moon phases require a one-day correction only once every 122 years.

Rose-gilt opaline, charcoal gray gold applied numerals with luminescent coating. White gold. Diameter: 40 mm. Height: 11.13 mm. Water-resistant to 30 m. Interchangeable solid and sapphire crystal case backs. Alligator leather with square scales, hand-stitched, shiny chocolate brown. Fold-over clasp. Perpetual calendar. Day, month, leap year and day/night indication in apertures. Date by hand. Moon phases. Sweep seconds.

Perpetual calendar with day/night indication. Day, month, leap year and day/night indication in apertures. Diameter: 32 mm. Thickness: 4.97 mm. Number of parts: 367. Jewels: 29. Power reserve: min. 35 hours - max. 45 hours. Winding rotor: 21K gold central rotor. Balance: Gyromax^®. Vibrations/hour: 28 800 (4 Hz). Balance spring: Spiromax^®. Hallmark: Patek Philippe Seal.