Arguably the most ubiquitous, yet still desirable Seiko divers watch of the past 35 years is the 6309-7040, the successor to the 6105 duo and produced from the late 1970’s to the mid-1980’s. While the newer watch retained the 150m water resistance of its predecessors, it added a screw-down crown and day/date complications to the movement. The 6309A is a very robust and very good 17 jewel automatic movement used widely by Seiko in both this application but also in numerous dressier models. It is perhaps not quite as high a quality movement as the 6105 but still much nicer than the 7002 and 7S26 movements that were used in the mainstream 200m divers produced from the early 1990’s through to present day.
The great appeal of the 6309-7040 lies in its beautiful, symmetric cushion case and in the classic dial and hand design. The dial features printed hour indexes rather than the embossed indexes of the 6105 but this is the only really obvious quality compromise with the watch in the hand (although of course a printed dial does not necessarily mean cheap!). These watches are in plentiful supply but unfortunately the majority have had dials, hands and inserts replaced by poor quality reproductions. The aftermarket dials in particular pale by comparison to a good condition original and are quite easy to spot, most notably from the quality of the printed text on the dial and the lack of bevel around the day/date aperture.
I’ve had several through my hands in the past two to three years, the best of which came from Australia with a very good original dial but with greyed lume from moisture ingress. I elected to have the dial and hands relumed while servicing the movement myself – one of my earliest attempts at a full movement service.
The second example worth reporting here was a much scruffier watch requiring a lot of attention. This one came with aftermarket everything and the first job was to replace the dial with a second hand, original Suwa dial and better quality hands. I also elected to replace the movement with a 21 jewel hacking 6306A taken from a rather poorly Japanese market Silverwave.
With movement, dial and hands replaced all that remained was to substitute the bezel insert with one of the higher quality aftermarket inserts available and to replace the crystal with one designed for the 6105 divers. The original watches have perfectly flat crystals but the addition of a domed crystal is a popular modification that I think enhances the appearance of the watch. You will notice I made the same change to the first watch above.
I think this one turned out particularly well! I really enjoy your blog and you have given me a little motivation to try a few things on my own. I also have a 6309 7040 that could benefit from a domed crystal and relume 🙂
Hi there I very much enjoy your posting !
And do you actually do restoration, servicing , customize watches for others ?
Are you able to provide a complete servicing / restoration/customize for a vintage Seiko diver 6159-7010 ?
Hi Keith, I’m afraid I only work on my own watches – sorry. Thanks for the kind words about the blog.
I like Seiko 6309 – 704L very much and I bought one in fairly good visual shape. Dial is 100% original, not reprinted, untouched, with just a bit of “patina” on one of luminescent round marker.
Now it is at my watchmaker’s for overhaul of a movement, and I don’t know what is a good overall result. So far, after proper cleaning and lubrication, he got positional error of +-20 sec (40 sec) for all 5 (or even 6) positions. I was hoping to get +-10 (total 20) of difference in 5 positions or at least +-15.
Amplitude stayed low, around 170, and he thinks only pallet fork looks a bit suspicious (was a bit rusty) and spring on balance wheel is just a bit distorted.
What do you think about this numbers?
Thank you in advance!
The timekeeping you can expect will depend on all sorts of factors, not least of which the condition of the mainspring, the general level of wear and the overall cleanliness of the movement. The condition of the balance hairspring is of course absolutely vital. If yours is misshapen then the timekeeping may be erratic and it will generally be much more difficult to get it running to the sort of level of consistency you are hoping for.
More generally, it’s rather difficult to say what might be a level of performance to aspire to from a 6309 but by coincidence, I’ve been wearing a 6309 powered watch for the past few days (this one) and it is now sat on my time-grapher, dial up, and running at 0s/d with 0.1 ms beat error and an amplitude of 229 degrees. Crown down it’s running a fair bit slower, and dial down a fair bit faster. My experience of 6309’s is that they are generally a bit trickier to get running quite as sweetly as the older 6 series movements and perhaps it is not realistic to expect better than +- 10 s /d from something with all of its original parts.
Hope that helps
I found a new original pallet fork, my watchmaker changed it and did a bit of work on hairspring.
Amplitude is over 190 now, and positional error is +-6 secs in 6 positions!
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