The Seiko 6138 is the bigger brother of the 6139: an automatic chronograph with an hour counter, launched in 1970. It powers some of the most distinctive Seiko chronographs ever made, including the ‘Bullhead’, the ‘UFO’ and the ‘Panda’.
Quick facts
| Spec | Detail |
|---|---|
| Caliber | 6138A (from 1970), later 6138B |
| Type | Automatic chronograph with hour counter, day and date |
| Jewels | 21 (some 6138B examples 23) |
| Beat rate | 21,600 vph |
| Power reserve | 45 hours (Ranfft, 6138A) |
| Movement size | 27.4 mm wide, 8.0 mm high |
Main references
| Reference | Nickname | Notes |
|---|---|---|
| 6138-0040 / 0049 | Bullhead | Crown and pushers at 12 o’clock, asymmetric case, about 43.5 mm; Craft + Tailored dates it to 1975 to 1978 |
| 6138-0010 to 0019 | UFO / Yachtsman | 44 mm lugless case, made about 1970 to 1978/79 |
| 6138-8020 | Panda | Two-register ‘panda’ dial chronograph |
What to check before you buy
- Serial against case. No 6138 should date before 1970. A Bullhead dated 1971 deserves questions.
- Reset to zero. Start, stop and reset the chronograph several times. The seconds hand should snap back to 12 every time.
- Dial and hands. Vintage Watch Inc advises checking fonts, spacing and marker positions, and making sure the hands are not repainted.
- Case edges. Over-polished cases lose their sharp lines. Sharp edges are worth paying for.
- Movement. Ask for a photo and look for rust or water marks.
Typical 2026 price for a running, original example in very good condition: $650 – $1,400 (Bullhead) (see the vintage Seiko price guide). Adjust for your watch’s condition and parts in the value calculator. To date it, read the serial number guide or check the Seiko caliber list.
Compare it with its single-register sibling in the Seiko 6139 guide.
Looking for one?
Garasi Opung, the Jakarta dealer behind this site, hand-checks every vintage Seiko before listing it. Browse the Etsy shop, the eBay store or garasiopung.com, and run any listing’s caseback through the Franken Checker before you buy, ours included.
Frequently asked questions
Why is it called the Bullhead?
The 6138-0040 has its crown and chronograph pushers at 12 o’clock, which look like a bull’s horns above the case.
What is the difference between the 6138A and 6138B?
Ranfft and Vintage Watch Inc describe the 6138B as the same chronograph with a modified switching mechanism. The UFO switched from the A to the B around 1972.
Is the Seiko 6138 a two-register chronograph?
Yes. Unlike the single-register 6139, the 6138 adds an hour counter.