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.
While creating the 89630 calibre, IWC’s present-day master watchmakers constantly re- ferred back to the old design blueprints that were their source of inspiration. But there was a significant challenge, as the moon phase in the IWC-manufactured 52610 calibre normally used for the perpetual calendar is located at “12 o’clock”. If the chronograph’s hour and minute coun- ters were to be placed there, the hands would go straight through the centre of the moon phase disc. The 89360 chronograph calibre, on the other hand, had no room for a moon phase. As a result, the engineers designed the 89630 calibre, combining the dual counters of the chronograph with the moon phase mechanism and displaying them on a single subdial. A glance through the transparent sapphire-glass back cover reveals the so- phisticated design of the movement, which has blued screws, a red gold rotor and various types of decorative polishing on the bridges.
The Da Vinci Perpetual Calendar Chronograph is available in two versions: 18-carat red 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 har- mony. 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 silver- plated and slate-coloured, respectively.
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 pro- grammed, 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, an- other 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.
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.
Although the contemporary Arnold & Son is now owned by the Citizen Group and continues to be revived in La Chaux-de-Fonds, Switzerland, the heritage of precision timekeeping, advancements in escapement engineering, and Breguet’s influence can still be felt with this timepiece. The Arnold & Son DBG Skeleton basically combines two motions, each with their own barrel, equipment train, escapement, and balance, united with a single winding system and one centralized second hand. Both dials for house time and GMT are powered by their own dedicated motions, permitting each to be placed independently via a double crown in 3 and 9 o’clock. Coolness factor apart, this also includes a practical advantage in being able to set GMT time into the moment, which can be particularly beneficial when dealing with time zones offset by half an hour as parts of India, Australia, and Canada.In comparison to the non-skeletonized variant of this Arnold & Son DBG we analyzed before, this incarnation sacrifices some legibility in order to better display that beautifully symmetrical movement. A ring of smoked sapphire crystal is employed for every dial to help attract the numerals more into focus against the hectic background without completely obscuring it, and it is a smart move. GMT time can also be differentiated through the dial’s usage of skeletonized hands and Roman numerals, compared to the Arabic numerals and strong hands featured on the house time dial. Unlike the previous version, the hands on the Arnold & Son DBG Skeleton are gilded instead of blued, which is visually a nice complement to the vulnerable balance wheels but also makes them difficult to see at a glance.