The Seiko “UFO” is not one single reference: it is a collector nickname for a family of vintage 6138 chronographs, including the often-cited 6138-0011. “Yachtman,” by contrast, appears in Seiko-associated marketing. If you are identifying one, start with its caseback reference and compare the dial, hands, bezel and movement together; the nickname or one matching detail cannot establish originality.
What is a Seiko UFO watch?
“UFO” is a collector nickname linked to the watch’s broad, saucer-like case. A collector reference guide groups five movement-case references under the name: 6138-0010, 6138-0011, 6138-0012, 6138-0017 and 6138-0019. In these designations, 6138 identifies the movement and the suffix identifies the case code. The 6138-0011 is a commonly recognized UFO example, but the nickname should not replace the reference when describing a particular watch.
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The same guide reproduces a period Seiko distributor advertisement that uses “Yachtman.” That provides evidence for the marketing name, but not for when collectors first began using “UFO.” Avoid treating the nickname as an official model designation or assigning it a precise origin date. Collector reference guide
When was the 6138 UFO made?
A collector guide found the reference in a 1969/1970 US catalog and reports that it disappears from catalogs in 1979. From catalogs and casebacks examined, its author estimates production at roughly 1970 through 1978/1979. This is a collector’s estimate, not an official Seiko production record or a serial-number dating database. The guide also reports period retail prices of ¥20,000 in Japan and $135 in the United States, but gives no verified catalog date for those figures. Collector reference guide
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What does the 6138 movement do?
The watch uses Seiko’s automatic chronograph caliber 6138. Seiko’s official history describes the 6138 as adding 30-minute and 12-hour totalizers to the 6139 configuration, placing it in the development of the company’s automatic chronographs. Seiko’s history of its automatic chronographs
The collector guide describes 6138A and 6138B variants across the family. It reports 21 jewels for the 6138A and 21 or 23 jewels for the 6138B family. For UFO examples, the guide says early watches used 6138A and that it observed a move to 6138B around 1972; the 6138B UFO examples it examined were marked 21 jewels. Treat that timing as the guide author’s observation, not a universal changeover date confirmed by Seiko. Collector reference guide
How do I tell whether a vintage Seiko UFO is original?
There is no single visual shortcut. The collector guide warns that replacement dials, bezels and hands are common, and that some watches combine parts from different examples. Compare the components as a set, and distinguish “consistent with a known variant” from “proven original”: the latter requires evidence beyond a nickname or one matching feature.
- Read the caseback. Record the full movement-case reference rather than relying on a seller’s “UFO” or “Yachtman” label.
- Compare the dial family. The guide groups examples into early JDM dials marked “Seiko 5 Sports Speed-Timer,” international dials marked “Seiko Chronograph Automatic,” and later JDM dials marked “Seiko Speed-Timer.” These are broad groups, not a universal timeline for every market.
- Check the movement marking. Compare the 6138A or 6138B designation and jewel marking with the claimed reference and variant. The guide records variation, so a difference needs investigation rather than an automatic verdict.
- Assess the hands and bezel alongside the dial. A plausible dial does not establish that the other visible parts are original. The collector guide documents mixed and replacement components.
- Use the serial or date code as one part of the comparison. Check it against the claimed period and market version, but do not treat a code alone as proof of authenticity.
- Ask about service and replacement history. A service record or disclosure of replaced parts helps explain what is original and what has changed. If the available evidence remains unclear, describe the watch as unverified rather than authenticating it from appearance.
Dial wording, water-resistance text and reference-number patterns vary by market and period, and the guide notes exceptions. A combination of reference, market variant, movement, dial and other parts is more informative than forcing every example into one fixed specification. Collector reference guide
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What strap fits a Seiko 6138-0011?
A 2025 collector bracelet-reference guide lists the XAA 541 bracelet at 19 mm for the 6138-0011 UFO/Yachtman. That width is a practical starting point when shopping for a strap, but it does not prove that a particular bracelet’s end links fit the case, or that the bracelet is period-correct or original. Check the actual watch and bracelet fit before buying. 2025 collector bracelet-reference guide
How to compare two 6138 UFO examples
Compare like with like before deciding which example is better documented. Keep the comparison specific to the watch in front of you rather than treating all UFO references and market versions as interchangeable.
- Full caseback reference and claimed market variant
- Dial family and exact printed wording
- Hands and bezel, including any disclosed replacements
- Movement version and jewel marking
- Service history and component-replacement disclosures
- Bracelet reference, width and end-link fit
Current pricing cannot be responsibly reduced to a figure from the available reference material: condition, provenance and market all matter. No production-volume or surviving-example statistic is established by the cited collector guide.
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