Gisbert Brunner and Christian Pfeiffer-Belli, in their encyclopedic book Wristwatches Armbanduhren Montres-bracelets (Koenmann, 1999), called the IWC Calibre 8531 "one of the best automatic movements ever built in Switzerland".  The famous watchmaker Donald de Carle, in his book Complicated Watches and their Repair (R. Hale, Ltd, reprinted 1999), claimed that  IWC's special automatic winding mechanism was "a simple and ingenious system, well constructed and beautifully finished".

Automatic wristwatches, as we know them today, were introduced in 1929 by Harwood. Many of the  mechanisms from the early 1930s, such as those produced by Rolls, Wig-Wag, Wyler and Autorist, had technical limitations. In 1931 Rolex introduced its "Oyster Perpetual" movement, which it patented in 1932 and which used a rotor whose swinging mass served as a unidirectional winder. By the late 1930s and  through the 1940s, other companies followed. The large producers of base movements, particularly companies under the Ebauches S.A. umbrella such as AS (A. Schild), Eta and Eta-Eterna, focused their efforts on the development of automatic winding systems. Donald  de Carle estimates that at least 200 patents for automatic winding mechanisms were granted between 1944 to 1955. 

IWC entered the race in 1944, when Albert Pellaton became its Technical Director and immediately commenced development of an automatic winding system. His first design, which was patented in 1946, never was produced. It employed two clicks and had historical antecedents in a proposal from 1780. Pellaton's second design, patented in 1950, resulted in IWC's Calibre  81. Only 1,800 of these movements were produced in 1950 and 1951. Rumors still float that a watch with that movement might be found somewhere. If a collector finds a vintage IWC automatic with small seconds, he will have uncovered a rare treasure.

Also in 1950, IWC introduced another automatic movement, the central seconds Calibre  85. This movement used the now famous Pellaton winding system, in which rollers (shown at left in red) oscillate between an eccentric cam, which causes two clicks (shown in yellow) to ratchet against a saw-toothed winding wheel. The system had many advantages: it was easy to disassemble for service and it  offered shock resistance. It also was efficient in winding,  both because of the ingenious design and because two jewels could be used as bearings due to the shock resistance. While the mechanism was unique to IWC and patented, its concepts had antecedents. Longines used eccentric winding in a 1945 model and Lanco had a hammer automatic with double lever winding.

In 1950 and 1951, a total of 8,400 Calibre 85 movements were produced. By 1952, IWC improved the design with the Calibre 852, depicted at right. This movement enhanced the Calibre 85  by  using a hairspring with a  Breguet overcoil and also had  a regulator for fine adjustment.  The height increased from 5.45 to 5.6 mm. The Calibre 852 was a great success, with 49,200 made in the next six years. A date model, the Calibre 8521, was introduced in 1953, and another 13,200 of those were made through 1958.

In 1958, IWC further improved its automatic movement with the introduction of Calibre 853. The corresponding calendar model, Calibre 8531, was introduced in 1959. In both instances, the changes were relatively minor and technical. Equalizing screws were included on both spokes of the balance. Improvements also were made to the barrel. 

Watches with these movements sold very well and relatively many were made, at least by IWC's standards. The Calibre 853 (shown at left) continued production until 1963 and the Calibre 8531 continued until 1964. During this period, a total of 140,400 were made of both the calendar and non-calendar models.

In 1964, IWC introduced its successor Calibre 85xx movement: the Calibre 854 and its companion Calibre 8541 with date. This movement was slightly smaller than its predecessors. Its diameter was reduced 1 mm and, more importantly, the movement was slimmed down from 5.6 mm in height to 4.85 mm (and from 6.4 mm to 5.9 mm in the date version). Because the movement was thinner, a shorter barrel was used, which had the barrel teeth in the middle of the drum. In addition, an exclusive IWC fine adjustment system was used in these movement.  Early versions continued to have 21 jewels, but later versions had as many as 25 jewels. 

In 1976  IWC began production of  the Calibre 8541B, which has a "Greiner" type collet. Due to new regulation machinery at the factory, the collet --a ring affixed to the balance staff and which hold the hairspring-- was changed, as was the balance staff itself. The Calibre 8541B  continued to be available for 20 years.

During this period, several variations were made of the Calibre 8541B, although the mainplate was not engraved with different calibre numbers. For example, some Calibre 8541B movement had a "second-stop mechanism" (what is sometimes called "hacking"). These were listed in factory records as Calibre 8541BS, but the movements still were engraved as "C. 8541B". The so-called "Jumbo Ingenieur" (Ref. 1832 in steel), of which reportedly only 978 were made in all metals with automatic movements, contained the Calibre 8541ES. This designation meant that certain movement parts were antimagnetic (the "E') and that the movement had a stop-seconds mechanism (the "S'). Again, however, this was not engraved on the mainplate.

Various surface treatments were used on the Calibre 85 family. The most predominant was nickel, as shown in the Calibre 854 at right, although  later examples of the Calibre 8541B were gold-plated. The last Calibre 8541B IWC automatic movement was used in the Ref. 1850, a special model with a hunter-style display back. This model was available until 1996 and used a gold-plated Calibre 8541B movement. At about that time, however, IWC's development group began designing  the Calibre 5000 movement, which finally debuted at the 2000 Basel Fair.

The Calibre 5000, which is used in the limited edition Portugieser 2000, carries on the tradition of IWC's great automatic movements. One could claim that it is not a direct descendant of the Calibre 85, since the Calibre 5000 also incorporates key elements from other aspects of IWC's heritage, including from the famous IWC Calibre 89 manual movement and IWC's pocket watch legacy. However, it is clear that the new Calibre 5000 preserves the tradition and, of course, includes the Pellaton winding system.

For a chart summarizing the technical characteristics of the Calibre 85 movement family, click here