Sometimes you really want to dig into the history of that watch you just found. For some brands you can easily get in contact with the brand and ask for some (free) information from the archive (more on that here). In other cases you just want a quick check on the serialnumber to determine the year that a watch is built. This is especially useful with military watches since these require the watches being built somewhere prior to or during 1914-1918 for the first world war or prior or during 1939 – 1945 for the second world war. I dare to say that most military watches offered on eBay actually are most certainly not.
I recently purchased a copy of Zaf Basha’s “Jaeger LeCoultre”, which is a great resource on JLC as a brand and a rundown of the best movements and watches they made in their rich history. I have quite a few books about watches but this one is by far one of the best and I would like to encourage anyone to find yourself a copy. (ISBN 0615223877)
On this page was a table with serial numbers per year, however I received a friendly request to remove it by it’s copyright holder. However I have permission to provide lookups, so if you want you can an email to firstname.lastname@example.org with your serial number and I will provide you with the correct year.
If you open up the case of your Jaeger, Jaeger-LeCoultre or LeCoultre wristwatch you can usually find a serial number like in this example below. The 269.000 serial number points to a production year of somewhere around 1943.
I hope this helps you out, please know that these lists are available for a lot of other brands as well. Success!