As we told you last week, IWC will be debuting their overhauled Portugieser collection at SIHH. For their all new Annual Calendar, IWC needed to develop a new automatic movement. The result is in-house caliber 52850 which runs at 4Hz, has 36 jewels and boasts a 7-day (168-hour) power reserve.

The new caliber features upgrades that will be seen across the entire 52000 caliber family. Including a slimmer rotor, and the bridges that are more open – allowing more details to be visible through the open caseback. The bridges are inset with a solid gold “Probus Scafusia” medallion. There is also an improved Pellaton winding system with a virtual wear-free component made of black and white ceramic.

The midnight blue dial/steel model (shown) features a sunburst finish, complimented by silver polished, leaf-shaped hour and minute hands, silver polished applied Arabic numerals, silver polished subsidiary hands against a circular guilloche pattern. Luminous hour indices. Fonts are printed in white.

While the movement is complicated, the dial layout is anything but. The purist design features a triple calendar indication (at 12 o’clock) for the month, date and day, each with their own aperture. In addition, the watch displays hours and minutes via the centrally mounted subsidiary dials for small seconds (at 9 o’clock) and remaining power reserve (at 3 o’clock).

The calendar switching mechanism automatically adjusts for the different number of days each month, however, unlike a perpetual calendar, it is unable to make the adjustment for February or take into account if it is a leap year. Therefore, it needs to be manually corrected once in February, and once during a leap year.

According to IWC, “For the development of the annual calendar module, IWC’s watch designers ensured that the correction could be carried out easily and conveniently using the crown. Thanks to this elegant solution, the engineers were able to dispense with a corrector, which would have compromised the Portugieser Annual Calendar’s purist design.”

The crown is non-locking, polished and features a relief engraved “Probus Scafusia” logo. And, thanks to the innovative movement design, no recessed caseband pushers are needed to correct the annual calendar. Instead, all functions are controlled by the crown.

The IWC Portugieser Annual Calendar is available in steel, in either a midnight blue (Ref. IW503502) or a silvered dial (Ref. IW503501), and in 18K red gold with a silvered dial (Ref. IW503504). The case measures 44.2 mm by 15.3 mm and is fully polished with a thin fixed bezel

All three references come with a black alligator strap and folding clasp. Water-resistance is 30 meters. An arched edge sapphire crystal with anti-reflective coating on both sides protects the dial.