The IWC Portugieser Eternal Calendar, reference IW505701, is IWC Schaffhausen’s first secular perpetual calendar. Its platinum case measures 44.4 mm in diameter and about 15 mm in height, with a box-shaped sapphire crystal over the dial, a sapphire case back and water resistance to 5 bar (50 m). The dial is made of glass with white lacquer applied to the underside, and the sub-dials and numerals are applied by hand. Inside is the in-house calibre 52640, an automatic movement with Pellaton winding that runs at 28,800 vph (4 Hz), uses 54 jewels and stores 168 hours (seven days) of power. Functions include hours, minutes, small seconds, a power-reserve indicator, the secular perpetual calendar with four-digit year display, and a Double Moon display.

A conventional perpetual calendar treats every hundredth year as a leap year and needs manual correction in 2100, 2200 and 2300. IWC added a 400-year gear wheel so the Eternal Calendar follows the Gregorian rule that skips leap days in three of every four century years. IWC states that the moon-phase display is accurate to one day in 45 million years. The watch was presented at Watches and Wonders 2024 alongside the new Portugieser Perpetual Calendar 44 in white gold and Armor Gold. It is fitted with a black Santoni alligator strap and a platinum folding clasp. IWC lists the price on request; Fratello reported a base price of about CHF 150,000 excluding VAT, set at spot rate.

The watch received strong recognition from the industry. It won the Aiguille d’Or Grand Prix, the top prize at the 2024 Grand Prix d’Horlogerie de Genève. Fratello’s Robert-Jan Broer described it as very impressive in person and quite wearable at 44.4 mm, helped by the thin bezel and box crystal, and praised the calendar and moon-phase engineering. He also argued that IWC had solved a problem that does not really exist, and suggested the regular Portugieser Perpetual Calendar as the more sensible purchase. Some readers criticised the glass dial for looking plastic in photographs. As of October 2026 the Portugieser Eternal Calendar remains in IWC’s catalogue and is offered on request, so it is in production.