Quick facts
- Caliber
- 6138(automatic chronograph)
- Jewels
- 21–23
- Beat rate
- 21,600 vph
- Hacking / hand-winding
- No / Yes
- Water resistance
- —Pending verification
- Crown
- 12 o’clock
- Production
- 1969–1979
- Modern equivalent
- —Pending verification
Variants
The 0049 was sold in the US; the 0040 was sold both in Japan, as a Speed-Timer, and abroad.
| Reference | Market | Day wheel | Status |
|---|---|---|---|
| 6138-0040 | — | — | Pending verification |
| 6138-0049 | — | — | Pending verification |
Serial decoder
Enter the six-character serial from the case back. We use 1969 to 1979 for the 6138.
Possible production date, not a guaranteed date or an authentication. Production date is not the purchase date.
Full decoder with caliber and case codePrice guide
Prices appear after our first sampling of sold listings in November 2026.
| Condition | Low | Median | High |
|---|---|---|---|
A · Collector | — | — | — |
B · Serviced original | — | — | — |
C · Running, unserviced | — | — | — |
D · Project or suspected franken | — | — | — |
Sampled —, n = —, eBay sold listings viewed manually.
Checks before you buy
Bullheads came in versions that look like swaps but aren't. Check the dial, hands and bracelet as a set.
Dial code and market A dial code that fits the market version; a 6138-0060T dial on a 0040 or 0049 case is normal.
A Japanese Speed-Timer dial on an export case without a story.
Sources: Collector guide. Our own photo comes with our first shoot.
Hands and lume Hands that match the dial version: luminous with a yellow seconds hand on export, white with a red seconds hand on the brown Japanese version.
Hands from the other version or from another model.
Sources: Collector guide; Foro de Relojes. Our own photo comes with our first shoot.
Case finish Distinct brushed and polished surfaces with crisp edges.
Rounded edges or a fully polished case.
Sources: Fratello. Our own photo comes with our first shoot.
Bracelet A Z040S fishbone on export watches, with matching end links.
A Helmet Z050S bracelet or mixed links. A stamped code alone doesn't prove the bracelet came with the watch.
Sources: Foro de Relojes. Our own photo comes with our first shoot.
Chronograph and calendar Both counters start, stop and return to zero; day and date quickset and change overnight.
A seconds hand that slips on reset, an hour counter that won't zero, or a dead date quickset.
Sources: Plus9Time; Watch Repair Talk. Our own photo comes with our first shoot.
Common faults and service
The 6138 is a column-wheel chronograph with an hour counter. Run every function before you buy.
The chronograph seconds hand slips when resetting; Seiko's 6138A/6139A technical guide covers the fix (Plus9Time)
A snapped hour fly-back lever stops the hour counter from returning to zero (Watch Repair Talk)
The chronograph seconds hand slips when you reset it
The hour counter won't return to zero
Hardened seals or signs of moisture inside
Seiko USA no longer services the 6138 and asks owners not to send it (checked 2026-10-26).
On Seiko USA's list of calibers no longer available for service; they ask owners not to send them (checked 2026-10-26).
Where to look
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Why it’s called the Bullhead
The crown and the two chronograph pushers sit on top of the case, at 12 o’clock, instead of on the right side. Turn the watch upside down and the pushers look like horns.
6138-0040 vs 6138-0049
Both are 6138 automatic chronographs with a 30-minute and a 12-hour counter and a fixed tachymeter bezel. Fratello’s 0040 has a Hardlex crystal; we haven’t confirmed the 0049’s, and some dealers list it as acrylic. The main difference is the market.
- 6138-0049: sold in the US. Plus9Time’s scan of the 1975 Seiko USA dealer catalog has a brown 0049 on the cover.
- 6138-0040: sold in export markets and in Japan, where it was a Speed-Timer. Fratello’s 0040 has an English and German day wheel.
The two main colorways are black with blue subdials and brown with gold subdials.
Dials and hands that go together
Mistakes here go both ways. One collector guide records the export dial code as 6138-0060T on both references, so a dial code that doesn’t repeat 0040 or 0049 isn’t a problem. The same guide lists Japanese Speed-Timer dials coded 6138-0070T and 6138-0071T.
The hands differ by version too. Export watches have luminous hour and minute hands and a yellow chronograph seconds hand. The brown Japanese Speed-Timer has white painted hands without lume and a red seconds hand. A brown Bullhead without lume on the hands may be exactly as it left the factory.
The bracelet
Export Bullheads came on the Z040S fishbone bracelet. Collectors on Foro de Relojes record Helmet chronograph bracelets (Z050S) and mixed links fitted to Bullheads, so check the end links fit cleanly and the links match. A stamped code alone doesn’t prove the bracelet came with the watch.
What usually goes wrong
- The chronograph seconds hand slips when you reset it. Seiko’s 6138A and 6139A technical guide covers this fault, according to Plus9Time.
- The hour counter won’t return to zero. One repair on Watch Repair Talk found a snapped hour fly-back lever.
- Old seals. Hardened seals and signs of past moisture turn up on watches that haven’t been opened in years.
Seiko USA no longer services the 6138 and asks owners not to send it. An independent watchmaker who knows the 6138 and 6139 is the route.
Sources
- Fratello, #TBT The Seiko Bullhead 6138-0040: name, colorways, Suwa dial, Hardlex, dates.
- Plus9Time, Catalog: 1975 Seiko USA Dealer Catalog and Seiko 6139A and 6138A Technical Guides.
- Seiko, Cal. 6138B parts catalogue: movement specifications.
- How to Buy a Seiko Bullhead (collector guide) and Foro de Relojes: dial codes, hands, bracelets.
- Watch Repair Talk and Hub City Vintage: faults and aftermarket parts.
FAQ
Why is it called the Bullhead?
The crown and the two pushers sit on top of the case instead of on the right side, so the watch looks like a bull's head with horns.
What is the difference between the 6138-0040 and 6138-0049?
The market. The 0049 appears in Seiko's 1975 US dealer catalog in brown. The 0040 was sold in Japan as a Speed-Timer and in export markets, in black with blue subdials or brown with gold.
When was the Seiko Bullhead made?
Fratello dates it to roughly 1973 and says both colorways, black with blue and brown with gold, were sold until 1979, when the 6138 movement ended.
Is there a modern Seiko Bullhead?
Seiko made Bullhead-style quartz chronographs in 2012, the SCEB009, SCEB011, SCEB013 and SCEB015, with a 7T92 movement. They're a modern take, not a reissue of the 6138.