still to be verified
In one line
The 6139 with a 12-hour counter added, 1.25 mm more height and one thing its older brother never had: hand winding. This is the calibre of the Bullhead, the Panda and the Kakume.
First things first: the nickname is not the reference
These watches are almost never sold by their number. They are sold by nickname, and the nicknames get mixed up with cheerful abandon: the same dial is listed as a "UFO" on one site and a "Panda" on the next. If you are going to pay the premium some of them carry, know precisely what you are buying.
UFO (or Yachtman) → 6138-001X · lugless case
Kakume → 6138-003X · square sub-dials
Panda → 6138-8020 · Baby Panda → 6138-8000
Jumbo → 6138-300X · Baby Kakume → 6138-8030
There are more: the 6138-0020 "Tokei Zara", a helmet-shaped case sold in Japan only; the 6138-700X with its twin slide-rule bezel; and the 6138-8010, blue, Japanese and so scarce that it is known simply as the "Holy Grail".
The nicknames do not always come from where you think, either. Kakume is Japanese for square eyes: the two chronograph sub-dials are square, and that is the whole mystery.
6138 against 6139: what you gain and what it costs you
They left the same Suwa workshop a year apart and share an architecture: integrated chronograph, column wheel, vertical clutch, Magic Lever. Three things separate them, and all three are in Seiko's own technical guide.
| Calibre 6138 | Calibre 6139 | |
|---|---|---|
| Chronograph counters | 30 minutes and 12 hours | 30 minutes |
| Hand winding | Yes, auxiliary | No |
| Thickness | 7.90 mm | 6.65 mm |
| Diameter | 27.00 mm | 27.00 mm |
| Frequency | 21,600 vph | 21,600 vph |
| Day and date | Bilingual, quickset | Bilingual, quickset |
| Hacking seconds | No | No |
| Arrived | 1970 | May 1969 |
You gain the hour counter, and you gain being able to wind it after a week in a drawer. You pay 1.25 mm in height, which tells on the wrist in cases that were never slim to begin with.
If you want the one that made history, the 6139 came first. If you want the one that is better to live with, this is it.
Where it comes from
Seiko began work on the 6139 and its brother in 1967. The 6139 appeared in May 1969 and the 6138 followed a year later, in 1970, on the same base with two additions: a 12-hour totaliser and — Seiko's own words, in the first line of the technical guide — auxiliary hand winding.
There were two versions. The 6138A of 1970, with 21 jewels. The 6138B from 1972, with a modified switching mechanism and 21 or 23 jewels depending on the model. Production ran to the end of the 1970s.
The cases are where Seiko let itself go. The Bullhead, with the pushers and the crown up at the top. The UFO, lugless, like a flying saucer. The Kakume, with square sub-dials. All of them sold under the Seiko 5 Sports Speed-Timer name, all of them with the same engine inside.
Three things almost nobody knows
- The second sub-dial counts hours, not minutes This is the most repeated confusion about the calibre. Seiko wrote it down with no room for doubt: the hour hand drives the 12-hour totaliser and the minute hand the 30-minute one, both cumulative. A 6138 will time a full working day. In 1970, hardly any other automatic could.
- Seiko's manual settles the winding argument Half the internet says these Seikos cannot be wound by hand. True of the 6139, false of the 6138. The 6139A technical guide says "Automatic winding". The 6138A guide says "Automatic winding (with auxiliary hand winding)". Same company, a year apart, and one phrase in brackets closes the case.
- This one has no running seconds either Both sub-dials belong to the chronograph, so on a 6138 at rest nothing on the dial is moving. The only way to tell it is running is to press the pusher. What it does have, and so does the 6139, is a day of the week in two languages that the owner could choose between.
Technical data
| Type | Integrated automatic chronograph |
|---|---|
| Chronograph control | Column wheel with vertical clutch |
| Diameter | 27.00 mm |
| Thickness | 7.90 mm |
| Frequency | 21,600 vph (3 Hz) |
| Jewels | 21 in the 6138A; 21 or 23 in the 6138B |
| Counters | 30 minutes and 12 hours, cumulative |
| Calendar | Day and date, bilingual day, quickset by turning the crown |
| Winding | Automatic, with auxiliary hand winding |
| Hacking seconds | No |
| Production | 1970 – late 1970s |
What a watchmaker checks before buying one
The same faults as the 6139, plus one. The chronograph centre wheel is the scarce part in this family and the one that decides whether a watch can be repaired or ends up as spares. Try the reset several times in a row: the hands have to drop dead on zero, and here there are three of them to watch, not two. The 12-hour counter is the one nobody tries and the one that fails most often.
If the chronograph hand comes off its post on reset, the tube is worn. If the return feels stiff, look at the hammer spring: they bend easily and are the usual cause of an incomplete reset.
And the biggest problem with this calibre is not mechanical, it is honesty. The 6138 is one of the most tampered-with vintage Seikos out there: reproduction dials, cases polished until the edges are gone, hands off another model, new bezels. A watch built out of four other watches runs just as well and is worth half as much. Buy the case and the dial before you buy the movement.
Watches that used it
- 6138-004X "Bullhead" — 44 mm, pushers and crown at the top
- 6138-001X "UFO" or "Yachtman" — lugless case
- 6138-003X "Kakume" — square sub-dials
- 6138-8020 "Panda" and 6138-8000 "Baby Panda"
- 6138-300X "Jumbo" and 6138-8030 "Baby Kakume"
- 6138-700X — twin slide-rule bezel
- 6138-0020 "Tokei Zara" and 6138-8010, both Japan only
The one that came first, with a single sub-dial and no hand winding, has a page of its own: the calibre 6139.