Longines Case Numbers: An Introduction

This thread is not intended to be a comprehensive account of the case numbers that appear on Longines watches. Instead, I hope that this abridged account will provide readers with a useful overview of the topic. Additionally, it should be noted that, throughout its history, Longines produced watches with locally-made (i.e. not Swiss) cases. This overview will not address locally-made cases.

1. The era of serial numbers: 0 to circa 5'000'000

Longines began its consecutive serial number system in 1867. On many early Longines pocket watches, the only immediately visible serial number on the watch is found on the inside of its case-back. See Figure 1. Serial numbers continued to be the predominant case-back marking into the 1930s.

Fig. 1. Silver-cased caliber 20B, invoiced in 1894.


2. The era of order numbers: circa 5'000'000 to circa 8'000'000

Some time in the early to mid-1930s, Longines began to mark some of its cases with order numbers. Confusingly, Longines seemed to use two different order number systems simultaneously. One system used 5-digit order numbers, while the other used 4-digit order numbers. Along with an order number, cases were marked with an individual number within the order. See Figures 2 and 3. Though I will have to check my records to confirm, these systems began around 18'000 and 1'000, respectively. Notably, solid gold cases continued to be marked with serial numbers into the early 1940s. See Figure 4. By the early 1950s, order numbers had largely been phased out. Again, I will have to check my records to confirm, but the highest order numbers I recall are around 23'800 and 3'400.

Fig. 2. Stainless steel reference 3645, caliber 25.17, invoiced in 1936.


Fig. 3. Stainless steel reference 3541, caliber 10.68Z, invoiced in 1936.


Fig. 4. 14K gold reference 4178, caliber 27.0, invoiced in 1940


3. The era of reference numbers: circa 8'000'000 to circa 15'000'000

Starting in the mid-1940s, 4-digit reference numbers began to appear on some case-backs. These reference numbers are generally between 5000 and 6000. As mentioned in section 2, reference numbers became the predominant case-back marking by the early 1950s. Along with a reference number, cases were usually marked with an "iteration number" and an individual number. See Figures 5 and 6. I am using the term "iteration number" to refer to the number beside the reference number. Though there are exceptions, it seems that earlier examples of a given reference tend to have lower iteration numbers than later examples.

Fig. 5. Stainless steel reference 5411, caliber 12.68Z, invoiced in 1952.


Fig. 6. Stainless steel reference 5356, caliber 12.68Z, invoiced in 1956.


4. The second era of serial numbers: 15'000'000 to present(?)

According to Stéphanie Lachat's book entitled, Longines through Time, The Story of the Watch, Longines began to mark its cases with serial numbers in 1969, once again. As far as I know, the 8-digit serial numbers should appear on the outside of the case-back. Case-backs from around this time seem to also have 4-digit reference numbers marked on the inside. See Figure 7. Beyond the early 1970s, I am entirely out of my depth, so feel free to contribute to the information presented thus far.

Fig. 7. Stainless steel reference 8271, caliber 332, source: https://omegaforums.net/threads/longines-30ch-530-numbering.93404/#post-1212916

Just checked my records, these are the order number ranges I've got:

5-digit order numbers: 18'087 to 23'711
4-digit order numbers: 1'009 to 3'610

Ah, right! I forgot about the big Weems/Lindberghs with 38'xxx order numbers. Thanks for the correction.

At present, I am inclined to consider these >38'000 order numbers anomalous. I do not recall seeing case-backs marked with order numbers between 24'000 and 38'000, have you?

I don't believe that I stated there is nothing in between. I simply have not encountered examples with order numbers that are in between. If you are willing, I would be curious to see photos of the case-backs with order numbers between 24'000 and 38'000. P.S. Just saw your latest post.

Apart from having seen very few case-backs with order numbers greater than 24'000, the examples that I have seen do not fit within the progression of other 5-digit order numbers. For example, one watch that I have seen with an order number of 38'xxx has a movement serial number that is typically found in cases with order numbers around 22'000.

I've seen the 5-digit order number system on other brands of the period - for instance I have a 1940s Cyma that has a 5-digit code above a two digit code in the case back (don't have a picture handy but will update when I have a chance to take one). Does this reflect a common system or "best practice" across different case manufacturers in this period, or did Longines share a case manufacturer with other companies?

@Seiji Thanks for posting these examples of 38'xxx order numbers. I notice that these three have silver cases. I wonder if all of the 38'xxx-marked cases you have seen are silver?

I am adding these photos for posterity.

Source: https://empress.cc/products/1938-longines-niello-0-800-silver-swiss-pocket-watch

That is a good observation. I also have a couple of Cyma/Tavannes watches with 5-digit numbers on their case-backs (see below).

I believe that Longines' case production in the era of order numbers was a mixed bag. Gold cases were produced by various manufacturers, which can be identified by maker's marks. At least some waterproof references were almost certainly outsourced, as they closely resemble cases used by numerous other brands. I could be wrong, but I am under the impression that Longines also manufactured some of their own cases. With regard to 5-digit numbers on case-backs, I am doubtful that there is a connection between Longines' order numbers, and Cyma/Tavannes' numbers. But who knows!

Source: https://omegaforums.net/threads/cyma-tavannes.30975/

Thank you. I hope so too.

Here's mine, from a Cyma Triplex with a 414Ka movement. Mid-to-late-1940s I would guess. This one stuck in my mind due to the 18000-series case number. Cyma, like Longines, is reputed to have made most of their parts in house. If this numbering system is analogous (rather than just appearing analogous) to the one used by Longines, I would guess that probably reflects a kind of organizational approach common in the industry at that time. Given that St. Imier and Tavannes are only about 20km apart (and Cortébert halfway between them), it's not a stretch to think that the companies exchanged personnel and ways of doing things across the industry of the time.

This makes sense, to me. I think that I was initially reluctant to accept the idea of a "best practice" as I do not know enough about Cyma/Tavannes' numbering system. For all I know, the 5-digit numbers are references. If we could find examples of very similar watches with different 5-digit numbers, this might rule out the reference number possibility. Also, I do not know if other brands used a similar system. If it were just Longines and Cyma/Tavannes, then I would be reluctant to call it a "best practice" or common system.

Nothing to add, just that enjoy the reading and the exchange between experts 😀
Thank you for posting this, always happy to learn more on Longines watches

I am glad to hear that you enjoyed reading the thread!

Is the number you called the "iteration number" the one sometimes stamped on the back of a lug?