The Da Vinci Perpetual Calendar Chronograph (Ref. IW392101/IW392103) is the first model in IWC’s history to combine a chronograph from the 89000 calibre family with the perpetual calendar’s moon phase display in a subdial at “12 o’clock”. To achieve this, both the moon and the shadow of the earth are depicted on a single disc and rotate beneath an aperture in the lower part of the subdial. Together with the other three displays, this new function creates a harmonious unit on the dial of the 43-millimetre watch. The Da Vinci Perpetual Calendar Chronograph is available in two versions: 18-caratred gold and stainless steel.
With its 43-millimetre case diameter and case height of 15.5 millimetres, the design of the Da Vinci Perpetual Calendar Chronograph is impressive yet carefully balanced. The crown and the two push-buttons are cylindrical and no longer as round as those of the Da Vinci Perpetual Calendar of 1985. Combined with the large lugs of the moving horns, they create an impression of overall harmony. Despite the many displays, the dial remains clear and uncluttered because the designers chose dark blue as the colour for the chronograph moon phase totalizer at “12 o’clock”. This firmly distinguishes it from the dial and three subdials of the red gold version (Ref. IW392101) and the stainless-steel model (Ref. IW392103), which are silverplated and slate-coloured, respectively.
For the chronograph, the designers likewise made no concessions. The hour and minute counters are combined in a totalizer at “12 o’clock”, which enables stopped times to be read off as if they were the time of day. This is a significantly more elegant form of aggregate timing than two separate counters. The blue central chronograph hand shows stopped times to an accuracy of one-eighth of a second. The chronograph has two push-buttons,which are used to start, stop and reset the hands, as well as for the flyback function. The movement itself is designed in such a way that the stopwatch can run continuously without diminishing the 68-hour power reserve.
The perpetual calendar works with the utmost precision: in 577.5 years, the display will diverge by just one day from the moon’s actual course. The perpetual calendar displays the date, month and day of the week on three subdials of the same colour at “3”, “6” and “9 o’clock”, respectively. A small window in the bottom left-hand section of the dial reveals the four-digit year display. Mechanically programmed, the calendar takes into account the different length of the months and even the leap years. Nevertheless, every 100 years (2100, 2200, etc.) a leap day normally due is omitted, which means that a watchmaker will have to advance the calendar manually on 1 March. In 2300, another intervention will be necessary when the current century slide with the figures 20, 21 and 22 will need to be replaced with a new one for the years 2300 to 2599.