As pilots spent longer time in the skies, the watches at the time proved inadequate in withstanding different conditions in the air. Pilots needed their watches to be able to deal with extreme temperatures, vibrations, different light conditions, and powerful magnetic fields. IWC brought forward their first ever timepiece designed for aviation purposes in the 1930s.

Mark IX – The originator of the Mark Series was the watch named Spezialuhr für Flieger (Special Pilot’s Watch). The name Mark IX was colloquially derived only after the Mark X was  developed. The hand wound timepiece had a high contrast, luminous markers, and a meticulously tested movement, the Calibre 83.

Mark X – The Mark IX was replaced by the Mark X, a model developed to stricter specifications. Apart from larger numerals,  many changes were added within the watch: a highly accurate movement for precise time-setting, a Faraday cage to protect against magnetism, and a stainless steel, waterproof case with a screwed ring — to protect the crystal from sudden drops in air pressure.

In the 1940s, the British Ministry of Defense (MoD) prescribed a set of requirements for military watches. Twelve companies complied with these requirements, among them Omega, Jaeger LeCoultre and IWC; and these watches would later become known among collectors as the ‘Dirty Dozen’. It was the Mark X that the MoD issued for military service.

In 1949, IWC developed its first ever pilot watch – the Mark XI. While the previous models were also used by the military, they were not pilot’s watches but ones built specifically for the British Army. The Mark XI meanwhile, was specifically built to help the Royal Air Force navigators during their dead reckoning duties

Mark XI – While designed from the outset for the use of RAF navigators, it was later on used by pilots as well. It’s characterized by the addition of luminous markers at the 3, 6, 9 and 12 arabic numeral hour markers. It also inherited the water and magnetic resistance of its predecessors.

Mark XII – It’s not until 1993 that the Mark Series continued, with the launch of the Mark XII. While this revival was virtually a replica of the previous model, it came the first self-winding movement in the series, hence the “Automatic” text on the dial; and also a date display.

Mark XV – In 1999, IWC launched the Mark XV, which many consider the Mark Series’ transition from a military watch to a civilian timepiece. It introduced a bigger size (38mm stainless steel case, from 36) and replaced the previous Jaeger LeCoultre movements with an IWC movement. The Mark XV also marked the end of the traditionally styled Mark model, because in 2006, IWC introduced its modernized successor.

IWC decided to revamp the Mark Series by giving them a more unified look.

Mark XVI – The case size grew to 39mm, the 6 and 9 numerals were dropped from the dial. The Arabic numerals took on a more modern and elongated look and the hands were replaced by broader Flieger hands from the IWC Big Pilot line.

Mark XVII – The case size grew further to 41mm, a distinctive vertical date display was added at 3 o’clock, and a newly developed steel bracelet with a fine adjustment clasp was added.

Mark XVIII – Bucking the trend, the case size was reduced to 40mm, the single digit date window also returned at 3 o’clock in a played down design; while the hour markers for 6 and 9 were added back to the watch face. This resulted in a more symmetrical dial and a design that’s reduced to only the essentials.