Towards the end of June 1975, Pink Floyd’s Dark Side of the Moon entered its 118^th week in the UK album chart whilst Wings tussled with The Carpenters for the number 1 slot.

The Glam Rock era was moving into its second phase, the likes of Slade, Marc Bolan, Roxy Music and Sweet giving way to Suzi Quatro, Wizzard and Sparks. In other news: in a nationwide referendum, the UK voted to remain a member of the European Community following the election of Harold Wilson in October of the previous year; the UK became an oil-producing nation for the first time; Jaws premiered in the UK, becoming the highest grossing film in history and Angelina Jolie Voight was born.

The 1970’s was an era of extremes in fashion and, yes, taste, with voluminous glittery bell-bottoms, platform boots, tartan waistcoats and ridiculous top hats battling it out with avocado bathroom suites and mustard paint jobs on the automotive output of that lumbering, strike ridden monolith that was British Leyland. While we might look back in horror at some elements of this period, for many of my generation, the 1970’s were arguably the best decade of all for music. In design more generally it was a mixed bag: the decade that gave birth to the Austin Allegro and Morris Marina was also the decade that produced the Lamborghini Countach and Lancia Stratos.

The consistent features of the early ‘70’s were boldness, colour and extravagant design flourishes and these elements seem to have provided a deal of inspiration in watch design too, particularly those conceived in the first half of the decade.

Acid yellows, burnt and vibrant oranges and dazzling blues all featured. And greens, deep turquoise, shimmering bluebottle greens. Take all of this, add a dash of Japanese quirk, and we dial up the Seiko 6139-7060.

I have something of an awkward relationship with the 6139, defined partly by the extent to which they impose themselves on my wrist in a slightly unwelcome way and partly by occasional difficulty I have had identifying and ironing out operational glitches during their servicing. In having serviced only a handful of these watches, my impression is that the tendency for inconsistent and downright truculent behaviour centres on the operational relationship between the chronograph wheel, with its vertical clutch arrangement, and the condition of the bridge that provides its support. We’ll see to what extent that is born out as we work our way through this current project.

Time I think to introduce our contender, a Seiko 6139-7060 automatic single register chronograph dating from June 1975, fitted with the 21 jewel version of the 6139B.

I’ve covered some of the history and technical aspects of the 6139 before but in short, it was one of the very first automatic chronograph movements brought to market (some would argue, the first) and features a vertical clutch chronograph wheel and quickset calendar (both day and date).

The complexity of the movement derives from the addition of the chronograph functions to the base 6106 movement but I would not say that it is especially sophisticated or refined compared with some of the other Seiko movements of the period I’ve featured on the blog in recent months. Nevertheless, in common with many of the mainstream Seiko movements of the time, it has proved to be remarkably robust yet it is this robustness that can be blamed for some of the difficulties these movements present when reviving them. That may sound like an odd statement, but longevity, even in robust designs, results in wear and with the youngest examples now at least 40 years old, most of these watches will have had multiple services, not all of which executed by competent watchmakers. With simpler designs, you can work around issues thrown up by slap dash servicing but a chronograph provides many more opportunities for the cack of hand to exercise their talents in ways that prove more challenging to correct.

In the case of this particular watch, as suggested by the photos above, I do not have much to fear on that front (or at least, the external appearance would suggest some complacency is in order). In fact, there is not much to suggest that the watch has seen 40 years worth of wear nor more than the odd service. There are no markings for example on the inner surface of the case back to suggest it has visited a watchmaker.

So let’s get stuck in. The first order of business is to remove the autowinder mechanism and mount the movement in the dedicated Seiko movement holder. The hour, minute and seconds hand come off in conventional fashion, but the minute register hand sits so close to the dial surface that the most prudent way to remove it is to gently lever up the dial from the movement until the hand pops off. With the day disk and date ring removed, the calendar side looks essentially the same as the 6106, barring the substitution of a couple of plastic parts.

Over to the train side of the movement, and dismantling proceeds without drama, and reveals no unpleasant surprises other than a very decent degree of tarnishing of some parts, most notably the centre wheel bridge.

However, in opening up the barrel to inspect the mainspring, we encounter the first sign that someone has been here before.

The mainspring is very clearly no longer a perfect spiral but has been badly distorted both in and out of plane. You can see the bends in the left hand photo and may be able to appreciate that the spring is no longer flat either, in the photo on the right. In short, it is beyond salvage and needs to be replaced. I doubt very much that it will have been installed in this condition from new, nor that it will have somehow acquired this eccentric shape on its own. Someone has made a thorough dog’s breakfast of extracting and reinstalling the mainspring at service.

A thorough clean of all parts and reassembly can begin. Depending on how I feel this usually means starting with the mainspring or any Diafix settings on the main plate and bridges. As there is only one Diafix on the 6139B (serving the escape wheel), I opt for that.

The mainspring presents a slight difficulty in that original replacements are almost impossible to source. The choice then is limited to recycling a spring from a junk 6139; finding a regular 61 series mainspring (i.e. those fitted to the 6119, 6106, 6105 etc) and hoping that they deliver the same power as the correct 6139 part, or trying a Generale Ressorts replacement of the correct dimensions. I opt for the latter by way of an experiment.

Assembly follows in reverse order to disassembly, starting with the setting mechanism, then over to the centre wheel and its bridge, the barrel, centre chrono wheel and third wheel followed by the barrel and train wheel bridge.

The chronograph mechanism comes together next starting with the L-shaped intermediate minute recording wheel holder, whose job it is to sit over the two jeweled settings on the train wheel bridge that serve the escape and third wheels and to provide the lower setting for the intermediate recording wheel.

The coupling levers, hammer and springs come next, ready for the chronograph bridge.

On goes the bridge, followed by the balance and its Diashock settings and with a bit of power into the mainspring, off she goes.

But as it turns out, somewhat unsatisfactorily. The problem is hopeless amplitude, a wavering timing trace and a reluctance to keep ticking for more than about 12 hours at a time. The finger of accusation points squarely to that foreign main spring and so off it all comes with the barrel and mainspring substituted for one I’d prepared during my last 6139 project but set aside for just such an occasion. Perhaps with some further experimentation with, or indeed without, braking grease might have improved matters but my patience with this particular project did not extend that far. In any case, with a correct but used mainspring installed, the amplitude is now hitting 235 degrees but the watch still proving temperamental, stopping at the 58 minute mark with the chrono running at lowish mainspring power. This time, I started to wonder about the chronograph bridge, whose intermediate minute wheel bearing looked a bit ragged on its underside. Any impediment to the smooth progression of the intermediate wheel can stop the chronograph because it provides too much additional resistance over that provided by the minute recording jumper spring when the minute register ticks over.

Rather than attempting to repair or replace the bearing, I opted instead to give a spare old stock 6138 chronograph bridge a try. This part has a jeweled bearing serving the intermediate minute recording wheel (see arrow below).

By a stroke of luck, the photo above captures the moment that the minute register ticks over. You should be able to see the chronograph finger making contact with one of the teeth of the intermediate minute recording wheel (1) and as the wheel turns, it simultaneous acts upon the minute recording wheel whose movement is regulated by the minute recording jumper at (2). With the new bridge in place, the movement is finally running as it should, with very good amplitude and displaying a flat timing curve and zero beat error.

With the movement set to one side, ticking happily away, I can turn my attention to the case. Some time ago, I bought a handful of Seiko old stock sample cases off Ebay, intending to use one of the cases for the ‘A little bling is no bad thing’ project a couple of years back. The cases came with their case backs but without bezel, pushers, glass or any other fixtures and fittings. One of these mid cases was a 6139-7060, fitted with a horseshoe case back and with a serial number dating from 1974. With a new bezel sourced some months later, all I needed was a project with which to use it. So my intention is to remove the inner bezel, spring, spacer and crystal gasket from the old case and transplant them to the new case together with a new crystal courtesy of Sternkreuz.

The inner parts of the old case can only be accessed by removing the bezel and crystal, aided by the helpful cutout on the bezel, positioned in this example to the left of the case.

Having cleaned the new case, we are set to unite the old with the new.

From top, moving clockwise: the inner turning ring with spring (this goes in first); the spacer ring comes next, on which sits; the gasket. The assembly at this point in proceedings is shown in the photo below:

A defuzz of the otherwise excellent gasket and we are ready to seat the new crystal.

Lastly, the whole lot is pressed into place by fitting the new bezel.

And we are onto the home straight. I won’t document the reassembly of the calendar side of the movement because I’ve done so on a number of occasions before, but we can pause to survey the completed movement with the dial spacer in position ready to receive the dial.

Note the minute register axle peeping shyly out between the 9 and 10 on the date ring. On with the dial next.

Then the minute register hand, taking great care to align it correctly with the minute markers on the sub-dial.

I let the watch run for a bit to ensure the minute register ticks over happily and while it is doing that, I deconstruct the crown gear and stem to fit a fresh crown gasket. This requires a quick exposure to one of the gas burners on the hob in the kitchen to loosen the grip of the locking glue securing the stem to the crown.

The gear is there to allow rotation of the inner rotating ring in concert with rotation of the crown at its resting position.

Satisfied that the sub-register hand is correctly aligned and ticking over nicely every 60 seconds, the remaining hands can be fitted. The profiled sweep seconds axle means that there are no real worries about alignment when refitting the seconds hand other than to make sure to press in the reset pusher when fitting the hand (aided by the dedicated movement holder).

All functions appear to be operating correctly and so we can now unite the movement with its fresh new case, initially without the autowinding mechanism in place.

This allows the autowinding mechanism to be fitted with the movement securely and safely held in place within the case.

A fresh case back gasket follows, screw down the case back, turn over and have a think about a suitable choice of strap.

I rather stupidly neglected to act on an opportunity to buy a correct new old stock bracelet for this watch and so instead I opt for an 18mm caoutchouc rubber strap, perhaps a bit of a left field choice, but somehow for me it works.

This is not quite the epitome of the 1970’s watch suggested in the preamble because it keeps its flamboyance slightly in check. However, while its colour scheme conjures up a certain degree of ‘Glam Rock’, its profile reveals a sniff of ‘heavy metal’.

Whatever sense of nostalgia is inspired by these watches, I admire this particular model for its self-confidence, its individuality and for the fact that it goes about its business of quietly flamboyant eccentricity without worrying too much about all the attention that is garnered by its more celebrated sibling, the Pogue.

Happy New Year everyone.