Usually for the ones that kept accurate records. Sometimes they’re compiled by brand aficionados, who attempt to combine all the bits of knowledge into one resource.Serial number charts are only available for a handful of manufacturers though. Sometimes they’re official resources. Dating by design and technical featuresThe first thing to check are serial number charts. Since your serial number falls between those two numbers, you know that your watch For example, Doxa used separate serial number systems for solid gold cases.Omega serial numbers are different for Speedmasters.Zenith changed their serial number system circa 1962. Different serial number systems within one brandKeep in mind, that it’s important to research the system of production markings specific to a brand. So, their serial numbers are also available. High-end brands like Patek Philippe or Vacheron Constantin kept (and still keep) excellent records.But you can also look up the reference numbers in the Omega Vintage Database. OnTheDash has entire lists of various models, with production years given.Omega kept archives that are accurate enough to date their watches by serial numbers. That’s because production years of a specific model are known.Heuer is a good example. Dating by reference numberThe documentation of some brands is good enough to come up with a rough date of manufacture. In case of many serial number resources for a brand, check the serial with all of them.
![]() Eterna Watches S Serial Number Falls BetweenIf that’s the case, you can contact the manufacturer although that’s usually expensive.Omega, Zenith, PP, and VC, for example, won’t tell you a thing, unless you order an extract from the archives. Extracts of the archivesSometimes, resources aren’t available or they don’t answer your questions. Bulova used a letter to mark the decade, a number from 0 to 9 to mark the year in the decade.Rolex sometimes has put the quarter or the month in Roman numerals, and the year in Arabic numerals on the case back.Omega placed the year of manufacture of a particular batch of cases immediately after the reference number in Speedmasters.For Doxa, the first two digits of the case serial number mark the year (only for watches made between 19). Dating by simple date codesSome brands, like Bulova, used simple means of marking the date of manufacture. Even if you know the movement serial.Obviously, not all of their watches are listed in there but unfortunately, that’s as good as it gets. Unless you were lucky and bought a presentation watch with an inscription of a date. Often, the archives weren’t kept safe.For example, Doxa’s archives were flooded somewhere around 1965 and a fire destroyed Cyma’s records.With Doxa, it isn’t that bad, although for pre-1940 watches it can be a challenge. Some brands were simply careless when it comes to keeping records.That’s where it gets harder. Zenith and Omega used to work the same way but sadly, not anymore.When was the movement made, what case should it be in, model details, where was the watch invoiced, etc.Generally, they’ll provide all that they have in their archive for a specific watch.Extract from the Archives from Longines What if the records are gone?That happens if the brand no longer exists, or was “reactivated” after going bankrupt. You don’t have to pay for the bad news.Longines provides information about all their vintage pieces at no costs at all. It wasn’t used on a larger scale though, except for WW2-era German military watches, where the specifications required a shock device. It became a standard feature around 1950-1952.The most popular one, Incabloc, was patented in the early 1930s. 1940s/1950s style in the 1960s/1970s? Yes.Before the early 1950s, the majority of watches had no shock device. 1940s style watches in the 1950s? Yes. TritiumIn the early 1960s, the much safer tritium gradually replaced radium. Unsigned watches are very common, especially if we’re talking about pocket watches.So, it’s another method that can work, but there’s a ton of exceptions. But the year of patenting a particular technical solution only tells you the earliest possible date a watch was made.It’s more useful when you’re trying to determine the manufacturer of a watch. You can easily look up patents on Espacenet. In this case, you can easily look up the patent registration date by looking up the patent itself in Espacenet.Sometimes there will be a number like a patent number but marked “Depose”. In the case of Swiss patents, the number is either marked with a Swiss cross or with the word “brevet.”Sometimes it’s only the cross, sometimes “brevet”, sometimes both. This means, that a watch is definitely post-1960.Omega Speedmaster 105.012 with the spaced T for tritium which tells you that it was made after 1960. Photo credit: Bulang&Sons Patent numbers and registered designsIf a watch has a patent number on any of its parts, it’s always a lead. A watch with that patent number has a T for tritium on the dial. This will rarely produce a result, but after all, you want to investigate every lead.Note that a patent number gives you the earliest possible year of production.A patent for a watertight case was registered in 1955. At least they aren’t available anymore.It also never hurts to check, if a number without markings indicating it as a patent isn’t actually a patent number. They can give you an idea of the period that the watch was made. No, this might not be the year your watch was made, but it’ll be close.Vintage ads also show you the original strap your watch was sold with.Vintage ad for Longines that mentions Christmas 1957 in the text Dating by calibreIt’s useful to know the production years of a particular movement. Vintage advertsEvery now and then, it’s a good idea to look for vintage watch adverts if you’ve matched the style of the watch with a decade.The date the ad was originally published is often mentioned. But it doesn’t have any extra numbers.It tells you that a part is protected by a patent, but it doesn’t tell you who registered the patent and when. Patent mark, but no numberSometimes, you can find the word “Brevet” and the Swiss cross on some part of the watch. So, with these 2 clues combined, you can date the watch to 1960.This only applies when all the other methods also point to the decade that a patent was registered in. a “date letter” corresponding to a particular yearEach assay office had its particular style of the “date letters”. Dating by case hallmarksIt works fine with gold, silver, and platinum British market pieces, cased locally. Especially if the manufacturer has used a batch of movements that was made a few years earlier. Stop dr cleaner from macA lot of inefficient designs couldn’t live up to that promise.The use of “water-resistant” or “water-resisting” was very uncommon before 1969, so you can assume that a watch marked “water-resistant” was made after 1969. Water-resistantWhile both terms have been used in the 1950s and throughout the 1960s, 1969 appears to be the date that “ water-resistant” became the common phrase.The use of “ waterproof” was eventually dropped because it’s impossible to 100% shield a watch from water at all times. The British hallmarks are well documented. No lume markingsIf a watch doesn’t offer any clues about its date of manufacture, and the lume markings aren’t there, you’ll need a Geiger counter. So, a watch with the “Ra SWISS Ra” marking will be later than ca.1960, but earlier than 1969. The use of radium lume was banned in the USA in 1969.In the early 1960s, some countries made it mandatory to mark the lume material on the dial.
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