The IWC-manufactured 89800 caliber, which made its debut in 2009, redefined the digital date display. The triple-disc mechanism in the perpetual calendar features large-format displays for the date and month and, slightly more discreetly, the leap year cycle. All are ingeniously synchronized. The IWC chronograph movement (based on the 89360 caliber), which has been enlarged to include the calendar features, is also going skyward: it is now the mechanism at the heart of the Spitfire Perpetual Calendar Digital Date-Month.
The IWC-manufactured 89800 caliber is an example of watchmaking skill at its most advanced. It has exquisite circular-grain decoration even in places you are unable to see. The perpetual calendar under the bridges requires absolutely no external adjustment, and is mechanically programmed to take the varying length of each month into account.
Two discs show the month. In extreme cases, then, three discs need to be advanced simultaneously on December 31. This calls for a lot of energy, and explains why the 89360 caliber comes with another very special feature: a spring-loaded lever is raised via a snail each day throughout the month, before dropping down smartly to its starting point at the end. The energy released is transferred via another lever to assist with the switching sequence at the end of the month.
A wheel train in the calendar mechanism controls the two perforated discs in the date display. The correct date is shown in digits from 1 to 31, and can be read off easily in the window on the left-hand side of the dial. The date here is January 18: the month (01) can be seen on the disc on the opposite side of the dial.
The perpetual calendar in the 89360 caliber is able to distinguish between normal years with 365 days, and leap years. The four-year cycle between leap years is shown in a window in the seconds dial (with a red L for the leap year) on the dial. In our example, the three discs show the date 18.01.2009 or 2013 (L+1) because the years 2008 and 2012 are leap years.
Advancing the dials of three displays simultaneously isn’t easy. We couldn’t overcome the laws of physics, but we’ve managed to use them cleverly.
Equipped with the IWC-manufactured 89800 caliber, the Spitfire Perpetual Calendar Digital Date-Month in its 5N gold case is the flagship of the second IWC Pilot’s Watch line to be named after the legendary British fighter plane. The mechanical chronograph movement records hours and minutes in a totalizer at 12 o’clock and seconds on the watch’s chapter ring. It also features a flyback function. The autonomous perpetual calendar has a large date and month display together with a – small – leap year display at 6 o’clock. The self-winding movement’s vital statistics: 28,800 A/h, 52 jewels, 68-hour power reserve.
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The Dream of Flying
Numerous special editions of IWC’s legendary Pilot’s Watches have been sold, with part of the proceeds going to the Antoine De Saint-Exupéry Youth Foundation and its partner organizations.