Reply With QuoteWow a superb example and write up Duncan, great ser # :)
ps: Don't let Jim see it lol.
I've had this Seiko 6139 in my projects drawer for many years but as usual I never seem to find the time to get my own stuff done! However I recently made a concerted effort to get this one completed as it deserves to be worn and get some wrist time
The watch I'm referring to is a very early JDM Seiko 6139-6000 "5" Sports SpeedTimer. You do see early SpeedTimers crop up for sale occasionally but more often than not they are fitted with a blue dial not the yellow one.
Most people know of the later yellow 6139 chronographs due to their link with astronaut Commander William Pogue of the 1970's Skylab mission fame, but another interesting fact about the calibre 6139 is it was one of the first automatic chronographs to be developed, in fact there’s a strong argument that it was actually the first auto chrono available to the general public. The race to produce the first automatic chronograph was coming to fruition at the end of the sixties and the two main contenders were the Zenith-Movado group and a joint effort from Breitling, Hamilton/Bren, Heuer/Leonidas and Dubois-Depraz. These watchmaking houses joined forces because it was felt that a single house wouldn’t be able to complete the job on the grounds of insufficient technology, manpower and budget. By 1969 the work was done and the Breitling group announced their caliber 11 on March 3, and Zenith announced their El Primero around September of that year. The thing was that Seiko quietly released their 6139 calibre chronograph at the beginning of 1969 with a distinct lack of fanfare, there are examples of this watch with a caseback date of February 1969 which suggests that perhaps they were the first to market with their offering.
These very early 6139a's had many differences to the later 6139b's and a few differences to later 6139a's.
Looking down on the movement with the chronograph bridge yet to be fitted you can see the basic differences between the 6139a and b, the truncated 2nd coupling lever along with the short stop lever spring, different reset lever and missing minute register transmission wheel which is part of the chronograph bridge on an "a" movement. There are other differences that aren't immediately obvious such as thinner first and second coupling levers, different train bridge shape and different centre chronograph wheel and minute register wheel lengths.
However there are a few differences between early and later 6139a's that I've documented over the years as a result of servicing hundreds them. For instance the centre chrono wheel on the very early 6139a's were steel coloured not the usual bronze or the later brass of the 6139b's, and the coupling lever spring has a defined curve on the stop/start lever end. One of the more unusual differences is the outside surface of the barrel wall isn't actually round, it's machined with facets around it's circumference.
I've only seen these barrels a handful of times on the very earliest calibre 6139 examples and it's not hard to understand why they soon changed to a smooth machine turned barrel wall, a lot cheaper and easier to produce I would imagine.
As I said my example has been in the project drawer with a shed load of my other early Seikos awaiting their turn on the bench and extremely I'm glad it's now completed. It dates from April 1969 so it's from the third month of production which means it could be anything from 32 to 88 days older than the ones that rolled off the lines on that very first day of production!
The dial has some small areas of damage, the typical blacking of any thin or damaged areas of lacquer but on the whole it's not bad at all. Again the inner bezel has some print loss on few of the minute markers and both the dial, hands and the inner bezel required reluming. The 6139a's had two piece sweep hands but what is less commonly known is the handsets from the first couple of months of production have a matt finish not a polished one.
The early inner rotating bezels also differ from later ones due to the fact they have their gear teeth on the circumference and later ones have smooth sides, they also don't utilise a helper spring between itself and the gasket support ring. Of course being a JDM watch it has a Kanji day wheel fitted.
The "notch" case needed a new crystal fitting so I fitted a genuine Seiko "flat" 330W18GN I had stashed away for when the day came.
Although the case difference between a 6139a and b is generally acknowledged as being the notch by the crown, the cases are actually slightly different dimensions, an early bezel won't fit on a later case for example.
Anyway the whole movement was stripped and serviced and NOS sweep and minute register hands were fitted as my example didn't have them when I acquired it.
I'm really pleased with the way it's turned out, it's comprised of 100% genuine original or NOS seiko parts and it's running beautifully with bags of amplitude (for a calibre 61xx of course!) and minimal delta. The timing report puts it as running at a predicted daily rate of +5.8 seconds per day but in real life on the wrist that translates to actually between +2 and +3 seconds per day.
As I don't have an original SpeedTimer bracelet for it I've got it on a NOS Swedefreak "Eastech" H-link which thinking about it are now probably rarer than an original one anyway!
I hope you've enjoyed this little study of the early Seiko calibre 6139a's and hope you may have learnt something you didn't know previously.
Last edited by Thewatchbloke; 23rd October 2020 at 18:55. Reason: Typo!
Wow a superb example and write up Duncan, great ser # :)
ps: Don't let Jim see it lol.
That’s a really nice watch and a great write up
Thanks
Last edited by Sinnlover; 19th October 2020 at 14:38.
Thank you for sharing that Duncan. Interesting, informative, and just plain enjoyable. Lovely lovely watch!
Sent from my SM-A105FN using Tapatalk
I really enjoyed that Duncan, thanks.
Cheers..
Jase
Great post Duncan, always enjoy these detailed descriptions and a really early example brought back to life
It’s so good to be able to read posts like this, Thank you
Excellent post.....very interesting!
Very facinating! Thanks for sharing your little jorney with this one. A little bit of me wish I became a watchmaker.
Great work Duncan, that’s a cracking watch!
I didn't know that there was a "pre-Pogue Pogue"! Many thanks.
Originally Posted by TheTigerUK
I know about this one John, and I love it....!
Very very nice indeed Duncan, and an excellent insight into a highly desirable watch!
Great write up and photos, thanks Duncan. I really enjoyed reading that.
Excellent write up Duncan, so interesting.
I would however slightly differ in my opinion re,
"joint effort from Breitling, Hamilton/Bren, Heuer/Leonidas and Dubois-Depraz. These watchmaking houses joined forces because it was felt that a single house wouldn’t be able to complete the job on the grounds of insufficient technology, manpower and budget.
IMO in reality it was simply that the micro rotor movement from Hamilton was available and could be mated with the Dubois - Depraz chronograph module.
Heuer and Breitling probably had nothing to do with the development (maybe supplied money?) and used the finished product in their watches.
Cheers,
Neil.
These are always my favourite TZ-UK threads... great stuff! Thanks Duncan for taking the time to write this up
Great work as always Duncan. Exacty how any of these 'projects' do you have in the drawer? It must be a proper Seiko treasure trove
Agreed. Love Reading stuff like thisSent from my SM-N960F using TZ-UK mobile app
Thanks Neil! However I don't believe it was quite as simple as mating a Dubios Depraz module to a Buren micro rotor movement even though it does sound like that's what actually happened!
The consortium of Breitling, Heuer/Leonidas and Hamilton/Buren was preceded by a request from Gérald Dubois (who headed the technical department at Dépraz & Cie a long time chronograph specialist) to Willy Breitling about getting together and developing an automatic chronograph. Dubois could see the financial benefits of manufacturing an automatic chronograph but Dépraz & Cie didn't have the funds to develop his idea. Willy Breitling was enthusiastic and they both set about getting Jack Heuer (Heuer/Leonidas) and Hamilton (who owned Buren) on board. It's true the Dubios approach preferred using a modular design which is something they had developed in the late 1930's, but the calibre 11 chronograph module didn't already exist, it was developed for the movement. They did mate it with an adapted Buren developed micro rotor movement because it a) saved time and b) it allowed the space for a rocking pinion to allow drive to be transmitted to the chronograph train. The whole development was codenamed project 99 and was carried out in absolute secrecy such was the perceived market gains that could be made by the successful developer.
There's a fascinating Watchtime article about how the three competing factions went about developing their versions of the automatic chronograph here.
Great read (and further reading links!). It was this era of Seiko that really got me “into” watches quite some years ago.
The race to bring to market the first auto chrono.! Sounds like a coming Netflix movie
I wonder if that same passion, collaboration and competition still exists between any of the big players now...
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Great stuff and a lovely watch!
"A man of little significance"
What a great write up. Thanks so much, I learnt a lot there.
Don't just do something, sit there. - TNH
Cheers for that Duncan.
I'm going to read the article now.
Cheers,
Neil.
Lovely resto Duncan, you done a fab job on my 6139 6002, not just a service but a brilliant re-lume and found some NOS parts too..
Bravo, Duncan - that's a cracker! Great info on the minutiae of the differences between the movements too!
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