Blog: IWC Serial Numbers

First published: 29 June 2025, last updated 16 July 2025.

I make additions and corrections to this web site frequently but, because they are buried somewhere on one of the pages, the changes are not very noticeable. I decided to create this blog to highlight new material.

Note that these articles also get updated, especially soon after they are posted when additional information may be added. Check the “last updated” date to see when the article was last updated.

The section below is from the page about IWC - The International Watch Company.

As always, if you have any comments or questions, please don't hesitate to get in touch via my Contact Me page.

IWC Serial Numbers

IWC Movement Serial Numbers: click to enlarge.

IWC have archive records of every watch made since 1875. Every IWC movement is stamped with a serial number, which is recorded in these archives. The serial numbers of cases are also recorded, and are different from the movement serial numbers. The records before 1884 are less complete and use a different set of serial numbers to those used from 1884 onwards.

The book about IWC by Tölke and King lists the serial numbers and dates of each batch of movements, and the calibre. The chart here based on serial numbers gives an idea of movement production after 1884.

The effect of the depression can be seen in IWC's production for the years 1932 to 1934. Only 600 movements in total were made in 1931, 1,200 in 1932 and 600 in 1934. None of these were 12 ligne movements. In 1935 production stepped up significantly to 4,800 movements, including two batches of 600 calibre 83. In 1936 10,800 movements were made, and by 1937 production was back to pre-recession levels.

When a Watch was Made

Given only the raw data in Tölke and King, it is natural to assume that the date recorded for the serial number is the date at which a movement, and by extension, an IWC watch, was ‘made’. However, this is not strictly the case, and the date a watch was made was sometimes a long time after the serial number was allocated. The parts of rough movements could be made by automatic machinery, whereas watch finishing required skilled manual work. In the early days, IWC produced thousands of raw movements, more than they were able to finish.

The first movements of a batch were finished when the serial numbers were allocated and received the first serial numbers from the batch. Subsequent movements were finished later, sometimes much later in the case of a slow selling design, and some were never finished.

For example, in an article about a watch with an IWC calibre 72 ‘Fish Tail’ movement in the Horological Journal for October 2022, it is stated that the watch was made in 1904, although it was not sold to Stauffer & Co in London until 1911. This presents a conundrum, because the watch movement bears the Stauffer & Co. trademarks of S&Co beneath a crown in an oval on the barrel bridge and the word ‘Peerless’ on the bottom plate. It likely also has another Stauffer trademark of the head and upper torso of a ram underneath the balance cock. These trademarks are deeply impressed, made by punches using a fly press.

However, in 1904 IWC did not have an order from Stauffer & Co. for the watch. Since IWC could not know that seven years later they would receive an order from Stauffer & Co., the trademarks would not have been stamped in 1904.

If the watch had been made in 1904, applying the Stauffer trademarks in 1911 would be expensive and impractical. The movement would have to be completely dismantled before the marks could be punched, and the affected parts re-gilded afterwards. There would also be a danger that punching the marks would distort the plates, affecting the alignment of the bearing holes, a particular concern for a movement intended to be very accurate. This would be poor business practice and would not be done by a well-run business like IWC.

The solution to this quandary lies in what is meant by the term ‘made’. Like most watchmakers at the time, IWC divided the production of a watch into two broad stages, which were similar to the English processes of movement making and watch finishing.

In the first stage, the major components of the movement were formed from raw materials: brass and steel. These components were the bottom plate, the bridges and cocks, and possibly the barrel and the train wheels. They were in the ‘rough’ state, similar to rough movements supplied from movement makers in Prescot to English watchmakers. There were no jewelled holes; the parts were not engraved or plated, and there was no mainspring and no escapement.

When IWC planned a run of a particular calibre, a batch of serial numbers was allocated, usually 600 or multiples thereof. The rough movements for the batch were got together and stamped with their serial numbers. Movements were then finished in batches of 12 as required to fulfil orders. Finishing a movement involved taking the raw movement and jewelling the holes, engraving and plating the parts, fitting the escapement, balance, and balance spring, as well as the mainspring. The movement was then timed, adjusted, and cased before being dispatched to the customer.

This explains the sequence of events involving the watch with the calibre 72 movement in the Horological Journal article. The serial number was part of a batch allocated in 1094 and the rough parts of the movement were machined and stamped with the serial number. These parts were then held in store until 1911, when an order was received from Stauffer & Co. The rough movement parts were removed from storage and stamped with the Stauffer & Co. trademarks before being finished and cased.

Most people would not say that a watch was ‘made’ when the rough movement was created and placed into stock, to be finished later, sometimes years later, as was the case with the calibre 72 movement described in the original article, or even never finished, as happened with some other calibre 71 and 72 movements. It is, therefore, misleading to say that an IWC movement was ‘made’ when the serial numbers were allocated. Most people would say that something is made when it is finished, not when it is begun.

Note that the serial numbers of IWC movements and cases are not the same. The movement number was allocated when the batch of rough movement components was laid down. Cases, particularly gold and silver, were expensive, so they were not bought speculatively but were ordered when a movement was being finished, which could be many years after the movement serial number was allocated. The case serial number was allocated by IWC when the case was received at the factory from the case maker.

If you have any comments or questions, please don't hesitate to get in touch via my Contact Me page.

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