The JLC Mark 11 is considered by many collectors and enthusiasts to be one of the finest military watches ever produced.
The JLC Mark 11 was specifically manufactured to aid RAF navigators to accurately pinpoint 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 that 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.
The MoD put out requirements for a navigation timekeeping wristwatch, that would have a highly accurate movement with hack-device, an inner soft iron cage forming a shield to protect the movement from magnetic interference, a stainless steel waterproof case with a screwed ring in order to protect the crystal from a sudden decrease of pressure, and a black dial with luminous hands.
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 was recalled after 12-months (later 18-months) for further testing. The Mark 11 was originally reserved for use by navigators while later it was also issued to pilots.
The Mk 11 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 Jaeger Le Coultre (JLC) and IWC 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. It is believed this was mainly due to the JLC’s inadequate shock resistance.
The last JLC Mk 11 was delivered to the RAF in 1953 and most were decommissioned in the 1960s.
It is believed that only around 2,950 JLC Mark 11s were produced for the RAF and genuine original examples are highly sought after and have become extremely hard to find.