Blog: Non-matching IWC Serial Numbers

First published: 29 June 2025, last updated 27 October 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.

Non-matching IWC Serial Numbers

If you have an IWC watch with Stauffer & Company trademarks and have requested an ‘extract from the archives’, you might have been disappointed to be told that an extract cannot be issued because the case is not original to the watch and was changed after it left the factory.

Because of this, it has been suggested that IWC sold bare movements to Stauffer & Co in London, who put them into English made cases.

However, the cases look identical to those of other IWC watches of the same date that can receive an extract, such as my 1906 IWC wristwatch, the case serial numbers look like those stamped by IWC at the time and are in the correct range for IWC cases made at that date.

The IWC archives do not show that IWC sold bare movements to Stauffer & Company. All the watches have cases listed, the problem with issuing an extract from the archives occurs when the movement and case serial numbers don't match what is recorded in the archives. Unlike some manufacturers, IWC used separate series of serial numbers for movements and cases.

In the IWC records of sales to Stauffer & Company, each watch has its movement and case serial number recorded. When a request for an extract from the archives is received, IWC find the sales record for the movement serial number. If the case serial number matches the record, then an extract from the archives is issued. If the case serial number is not the one listed against that movement serial number, the case is not the one that the movement was in when it left the factory and an extract from the archives cannot be issued.

I noticed some time ago that non-matching movement and case serial numbers seems to happen only to watches with gold or silver cases made during or after 1907. Coincidentally, British hallmarking laws changed on 1 June 1907 to require that all imported gold and silver watch cases be hallmarked in a British assay office.

When the cases are gold or silver, they have British import Hallmarks, showing that they were not made in Britain. The cases carry the sponsor's mark ‘CN’ in cameo entered by Charles Nicolet, the owner of Stauffer & Co at the time. A sponsor's mark has to be stamped on every item submitted for hallmarking. It identifies under whose responsibility the item is submitted, it does not show who made an item and can be entered by someone completely unconnected with its manufacture.

If all watches sold by IWC to Stauffer & Company were cased at the IWC factory, it seems most likely that for watches with gold and silver cases, Stauffer & Company removed the movements, stamped the sponsor's mark and sent the cases to be hallmarked. It appears that they did not record the individual movement and case serial numbers, which were not the same. Some manufacturers stamped the movement serial number in the case so that the two are the same, but IWC did not. IWC movement and case serial numbers are not the same.

When the watches were reassembled after hallmarking, because the case serial numbers were different from those of their original movements, there was no easy way to match them up, and movements were not always put back into their original cases.

This would explain why IWC watches with gold and silver cases sold to Stauffer & Co. during and after 1907 often have non-matching serial numbers and cannot be issued with an extract from the IWC archives. Watches with base metal, oxidised steel or nickel alloy, would not be similarly affected because their cases were not required to be hallmarked and the watches were not dismantled by Stauffer & Co. after receipt from IWC before sale to retailers.

To prove this idea, I need more data. If you have an IWC watch with British import hallmarks from the year range 1907 to, say, 1920 and would like to help, please send photos showing the movement and case serial numbers and hallmarks to . Please send photos of the whole movement and case, not just the serial number.

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

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