The IW503801 by IWC is the Antoine de Saint Exupéry version of the Perpetual Calendar Top Gun IW502902 watch, with the differences being the tobacco brown dial, the display caseback, the Santoni strap with cream contrasting stitching and orange lining, and the calibre.
The movement is the in-house 52610, visible through the sapphire caseback. This has the conventional single-moon phase display. Other significant features of this movement are the twin mainspring barrels that offer excellent stability over the full 7 days of power reserve, a solid gold rotor, and a balance frequency of 28,800 vibrations per second (4 Hertz). The case is also slightly slimmer than the IW502902, at 15.5 mm. The oscillating weight is marked with a medallion bearing the initial A for Antoine.
This perpetual calendar has become an IWC classic. Originally designed by Kurt Klaus in the mid 1980s, it is notable for the fact that there are no caseband pushers: the watch keeps date, month, year and moon phase synchronised to perfection, and any adjustments are performed from the crown. The digital year display will keep going until 2299, at which stage the owner will have to take the watch back to IWC who will replace the century slider (supplied with the watch). After this operation it will display years up to 2499. Another adjustment will be required about once a century, from 2100, when the leap year cycle skips a beat.
The watch is a limited edition of 750, price €29,300 incl. tax, £19950 incl. VAT. Available from April 2016.