In 1950 IWC released its first generation automatic movement (81) designed by IWC’s Technical Director Albert Pellaton who came up with an ingenious pawl-winding system. The calibre 81 had a sub second design that was almost instantly dropped for the sweep second version calibre 85. In 1952 the movement had minor upgrades and was renamed 852 the following year a date variant calibre 8521. This was produced until 1958 when the updated 853 and 8531 was introduced, this movement lasted until 1964 when it was replaced by calibre 854-8541. The 8541 stayed in production all the way up to 1990.
When IWC released their first version of their new automatic movement in 1950 I doubt they would imagine the basic design staying production as long as it did. Check out the movement review and service video of a 8531 on the link below: