A Seiko 6139-8002 from February 1972

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I bought my first Seiko 6139 chronograph in the summer of 2008, I think from an eBay seller in the Philippines.  It was a charismatic, well-proportioned hunk of steel, very much a product of the early 1970s but having suffered to an extent from the joint attentions of father time and the elbow grease of production-line eBay fettlers.  Nevertheless, my watch kept reasonable time, its chronograph functioned correctly, although the reset required two pushes to zero the second hand, and its case had thoughtfully been subjected to a lovely polish, bringing the unsightly brushwork and sharp edges to a lovely, soft and brilliant shine.

That watch was a February 1971 Seiko 6139-8002.  I kept it for sixth months and then sold it for the princely sum of £70 including Royal Mail Special Delivery.  Fast forward 13 years, and I find myself in possession of another 6139-8002, this one dating from February 1972 and fitted to its original bracelet.

This model appears to have been produced for just two years, appearing in the Japanese market catalogue in 1971 and 1972 only and seemingly in just two variations.

Although the production date of the present watch is a year later than that first eBay purchase, at the time of writing, it is 12 years older in terms of what we might reasonably expect the passage of time to have inflicted.  An assessment of the condition suggests that externally, this watch bears the scars of normal wear, not abuse.  Its case has not been refinished but rather its edges and brushwork have just been softened by the gentle erosion that comes from handling and from the friction of clothing and typical interactions with hard surfaces.  The dial and hands look to be in excellent condition, barring some chipping to the white paint at the end of the minute hand. 

The watch was running, which is always a good sign, but the chronograph was unresponsive to attempts to stop and reset.  In other words, depressing the upper right pusher had no effect on the continuing operation of the chronograph.  Removing the caseback provides our first look at the movement.

Everything appears present but heavily tarnished with the sort of patina and dirt that comes from many years since the most recent watchmaker intervention.  In order to remove the movement from the case, we have first to remove the crown (of course) but also the movement ring and the two pushers.

Another testament to the long passage of time since this watch was last serviced is the very grungy condition of the pushers.

The final step before removing the movement is to detach the autowinding mechanism.

At this point, we can tip the case over and seat the movement into the dedicated movement holder.

This provides an unrestricted view of the excellent dial together with clearer sight of the chipped paint at the end of the minute hand.  With the dial and hands removed, we can take a quick peak to the rear of the dial to check out the date stamp.  The imprinted ‘19’ tells us that the dial was made in September 1971, 5 months prior to the manufacture date of the watch itself as indicated by its serial number.

A closer look at the minute hand reveals that indeed, a line of paint towards the tip on one side has been chipped away.

My approach to correcting this blemish will be to apply some Humbrol white acrylic gloss paint using the tip of a fine, sharpened oiler and to sand it down once cured.

The semi-naked dial-side of the 6139B movement reveals one of the sources of its elevated 21 jewel status compared to the lesser 17 jewel variant:  a Diafix setting serves the escape wheel where a simple jewelled bearing suffices in the 17 jewel version.

Returning to the train side, I have removed the balance and we can take a look at the chronograph bridge, noting the wear to the plating on one side caused by contact with the winding weight.

The issue I noted earlier with the failure of the chronograph to stop is quickly diagnosed as a loosely fitting chronograph bridge that was either not fully tightened down by a previous watchmaker or had worked itself loose (righthand arrow, below).  You might also just be able to see that the bushing serving the intermediate minute recording wheel has been dislodged out of its hole, possibly as a result of my initial attempts to tighten down the bridge not having realised that the recording wheel was not properly engaged with the hole at the centre of the bushing.

Removing the screws entirely, exposes the chronograph mechanism and in particular the vertical clutch and pillar wheel that define the design philosophy of this chronograph movement.

We get a better view of the damage to the bridge in the photo below, the inset also showing a dimple to the underside of the bushing created by the tightening down of the bridge with the intermediate wheel pivot not located in its hole.  I believe that to be historic because my initial attempt to tighten it down were tentative and quickly revealed the problem with the failed location of wheel pivots.

I have documented the dismantling of these movements on numerous occasions in the past and so we shall skip the detail of that here, noting simply that I encountered no further evidence of obvious faults or damage, aside from one issue that I shall get to a little later on.

The mainspring appears not to have seen the light of day since February 1972 which makes me wonder whether this movement has ever been properly serviced before, notwithstanding the clear evidence of interference with the chronograph bridge.

The mainspring, uncoiled, looks to be in excellent condition and so will find its way back into its cramped but freshly cleaned quarters in due course.

Meanwhile, I set about dismantling the case, a task that requires first the removal of the bezel.  The bezel is removed by locating the cut-out on its underside and then carefully levering it off, taking care to minimise damage to the brushing on the upper side of the case.

The case is very dirty but otherwise free from corrosion.

This marks our half-way point.  The cleaning all parts follows, including the case, and I set to one side fresh gaskets for the case back, pushers and crown and locate a new crystal.

Following the cleaning process, reassembly, starts, as is commonly my favoured approach, with the assembly and lubrication of the Diafix settings, in this case just the one serving the escape wheel on the dial side of the mainplate.

And as is my habit, next comes the mainspring, cleaned and re-installed into the cleaned and lubricated barrel.

Reassembly of the gear train and chronograph was simplified by my decision to replace the damaged and worn chronograph bridge with a new part (bottom right, below) that I have been saving for a rainy day.  The minute register jumper spring will need to be transferred from the old bridge to new a little further down the rebuild process but at this point, everything is on track.

At this point, with the cannon pinion and setting parts fitted, we are in a position to test the running of the movement.  However, the additional fly in the ointment that I alluded to earlier needs addressing.  The balance wheel was quite badly distorted out of plane and in situ exhibits an exaggerated up and down wobble as the wheel oscillates back and forth.  This annoyance provided my first opportunity to make use of a balance wheel truing tool that I have had for years but never used.

The balance wheel is removed from its bridge, and its pivots located in holes in the tips of two claws emerging from the arms of the tool (pictured above).  The arms are closed up carefully by rotating the adjustment wheel and the gauge the emerges from the centre of the tool is then adjusted so that it sits as close as possible to the high point in any buckle to the balance wheel.  Clearly, a significant buckle will mean that this distance will shrink and grow as the wheel is rotated.  We can see the extent of the problem in this case in the animated gif below.

Correcting the distortion requires the position of the high point to be noted, the wheel rotated 180 degrees and then gently manipulated downwards at that position.  This process is repeated, each time moving the measurement arm closer to the wheel until no further perceptible deviation occurs as the balance is rotated.

Satisfied that I had corrected the warped balance wheel, I refitted the wheel to the balance bridge, the bridge to the movement and confirmed that the movement now ran with no significant wobble from the balance wheel.  Encouraged by the success of this operation, I proceeded to refit all of the remaining setting and calendar parts.

Fitting the hour and minutes hands is achieved in the normal way but the minute register and seconds hand need the movement to be fitted to the dedicated movement holder to allow the reset button to be held depressed while each is fitted.  The photo below shows the minute register hand fitted and the seconds hand being aligned prior to being pressed home.

With that done, we can review the dial straight on to assess the alignment of the two hands in its reset condition.

We can turn our attention to the reconstruction of the cleaned case, starting with our blank canvas mid-case, freshly scrubbed and looking peachy.

I have a Seiko new old stock 320W28GN set aside for this watch and so with the crystal gasket cleaned, we can set the new crystal into position.

The crystal is sealed against its gasket by the external force exerted by the bezel.  One of the other parts I have been saving for this project is a new old stock bezel.

I cleaned the bezel (it may be new old stock but that does not mean it might not benefit from a good scrub after 50 years sat around in flimsy paper packaging), positioned it with its cut-out oriented towards the 9 o’clock position and pressed it into place with a crystal press.

With that done, the mid case is now ready to receive the movement.

Before re-casing the movement, we just need to pay some attention to the condition of the pushers, one of which was somewhat bent out of shape.

I straightened the pushers as best I could, fitted fresh gaskets and then set about re-casing and completing the assembly of the movement.

I demagnetised the movement and performed a rough regulation at this point to assess the condition and performance of the movement in situ.  Although it was running a little fast after this first pass (+15 to +18 sec/day), the beat error was negligible (0.0 to 0.3 ms, the latter in the crown down position) and amplitude varied from a low of 237 degrees (crown down) to a high of 258 degrees (dial down).  This is the best performance I have had from a 6139 in terms of amplitude and positional consistency (± 3 s).

After a further regulation to the timing, I refitted the case back and assessed the finished article.

The bracelet still needed a clean and so some time in the ultrasonic bath and a good scrub soon brightened that up and I could fit it to the watch and declare this project complete.

Although this particular 6139 variant does not enjoy the same iconic status as the classic Pogues, it has a very appealing, and I hesitate to suggest, manly vibe.  At 40mm across, it is a decent size but it’s not much larger top to bottom and so sits very comfortably on the wrist, in spite of its relative thickness. 

I enjoy its steely, rounded, machined appearance, its black dial peppered with green, orange, yellow and red highlights.  This is a watch born of the 1970s, just showing some hints of the glam rock flamboyance that would emerge a year or two later.   But it is also subtle, utilitarian, complex in form and above all rather unique.