The Mark 11 was specifically manufactured to help RAF pilots to accurately pin-point their intended targets. RAF bombing raids throughout the Second World War had been notoriously inaccurate. An investigation conducted in 1941 revealed that only around a quarter of the number of bombers which claimed to have attacked their targets actually did so. Other investigations concluded that more than 95% of bombs missed their intended target by more than five miles. The cause of this was simply due to the lack of precise navigation.
Consequently, the old system of “dead reckoning” (determining your present position by projecting your course and speed from a known past position) was abandoned and the focus turned to astronavigation which required an extremely accurate timepiece.
Upon delivery, the Mk 11 was subjected to an exhaustive 44-day testing period for ‘Navigator Wrist Watches’. Each batch then had to be sent to the chronometer workshop of the Royal Greenwich observatory in Herstmonceux. All watches had to be sent there from active units for maintenance as well. These ‘fitness’ tests entailed a 14-day period rating in 5 positions and at least two temperatures, plus further tests for ensuring the antimagnetic and waterproof properties of each piece. After passing these tests, each watch marked for a 12 month interval were the tests had to be run again. The Mark 11 was originally reserved for use only by navigators while later on it was issued to pilots as well.
The Mk11 was introduced into the RAF and the FAA (Fleet Air Arm) in 1949 and into the RAAF (Royal Australian Air Force) in 1950. At first IWC and Jaeger Le Coultre (JLC) produced these watches. However, having bought 2,000 Mk 11s from JLC in 1949 the RAF decided to buy only the IWC Mk 11 from 1949 to 1953, when the last RAF orders were placed. The last IWC Mk 11 was delivered to the RAF in 1953 although it was not officially decommissioned until 1981.