IWC started focusing on the production of technically advanced watches built specifically for aviation at a very early stage, becoming a true pioneer in this field. Progress made in aviation and navigation had created a growing need for rolex replica watches that offered maximum reliability under the toughest conditions. Ernst Jakob Homberger 1955, IWC managing director during the 1930s, had two sons who were so passionate about aviation that they decided to manufacture IWC's first special watch for pilots in 1936. The replica watches, containing Caliber 83, had a shatterproof crystal, high-contrast hands and numerals, a rotating bezel with an index for recording short periods of time, and an antimagnetic escapement. It was also highly resistant to temperature fluctuations, ranging from –40 degrees Celsius to +40 degrees Celsius. In response to a rolex replica sale product requirement from the British government, IWC developed a service watch for pilots of the Royal Air Force. The technical specifications stipulated by the RAF were very rigid, including a requirement that the replique montres movement had to be protected against magnetic fields. Production of the now-legendary IWC Mark 11, with Caliber 89, started in 1948. In November 1949, the watch was supplied to airborne personnel of the RAF and other Commonwealth nations and remained in service until 1981.