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The recent acquisition of some ultra-thin calibers from other makers has allowed me to more fully appreciate what is rightfully (at least from the point of view of the one tasked with repairing it) termed a “complication”. Ultra-thin calibers, and their associated casing parts are an answer to the question, “what does one do away with when trying to eliminate all but the essential?” Seiko is rightfully associated with robust calibers that are relatively easy to service, and designed with forgiving tolerances in many respects. However, as with any pigeonhole, this does not capture the true scope of the brand's capabilities.


I was very excited to see an email one morning from eBay, pleasantly informing me that an auction matched one of my saved searches, one that typically did not produce many hits. I’d been aware of the caliber 6810 for a few years, but only vaguely. It has been around since the late 60’s, but is still used today in some astounding dress watches, many of them in precious metal cases and with skeletonized, hand-engraved movements. Much of what I knew about the caliber came from this great article, which you might want to enjoy before reading further; it offers an excellent understanding of how Seiko is using the 68 series today, as well as how skilled the watchmaker(s) (not sure if there are others outside of Mr. Mamoru Sakurada, who has been with Seiko since 1965!) is/are who assemble and adjust them:
http://home.watchprosite.com/show-forumpost/fi-17/pi-4547558/ti-702888/s-0/


Otherwise, I have no listings of the caliber family in my technical guides or parts listings, so there wasn’t a lot of information to go around on it. Thanks to garfre’s sharing of his vintage Japanese Seiko catalogs (bookmark this link: http://www.thewatchsite.com/index.php/topic,17038.0.html), I was able to put some names to faces, in that I could see some models that used the 6810 movement:



I had also seen a picture of the watch on the left before, and loved the bold lugs. If you notice, the price of the two 6810-equipped watches (2 hands, manual wind only, on a strap) was quite a bit more than a 3-hand, day/date automatic Grand Seiko Special model on a bracelet:



So months (years?) go by after deciding I should keep an eye out for all things 6810, and suddenly a 6810-0080 appears on eBay (the one on the right of the second previous picture above). Sporting an after-market mesh bracelet whose sharp edges had cut into the lugs (can we all agree to never use those anymore?), it was advertised as coming from a yard sale, missing the crystal, and running albeit “temperamental”. Chancing the odds that instead of a personality issue it was actually just in need of a servicing, I placed a bid based on emotions, lacking common sense and decency compared to my usual small-time “parts or repairs” buys, and made it mine. I blame my curiosity, and also soothed my conscience by saying that the entrance fee to any modern-day 68-based timepiece is in a realm of magnitudes more. Whatever works…


The watch arrived, and I set about examining it with baited breath and a little bit of wonderment. Apart from a hairspring that required adjustment (one of the thinnest, most pliable hairsprings I’ve dealt with in recent memory), and a third wheel with a scored pivot, there were no catastrophes that would turn my purchase into a (albeit thin and light) paperweight. The dial had some marks and damage around the edge from slight moisture intrusion and the lack of a crystal for some time, but nothing upsetting. I sourced a generic sapphire crystal in the thinnest dimension I could find (.8mm), found a Seiko crown post gasket that fit the crown and tube, and a thin alligator strap to match the catalog scan as best as possible (I get a kick out of period-correct attachments). Otherwise, no parts were replaced, nor could they have been, as my searches with my usual sources mostly turned up “no such listings” when inquiring about either the caliber 6810 or the case number 6810-0080. So if any of you located outside the USA have listings of such, I’d appreciate hearing about it- I’d at least like to source a genuine crystal at some point, which may have been used by another, more common case reference. I’m also on the look-out for a new third wheel (part number 0231019), the scored pivot doesn’t seem to be affecting amplitude or power reserve yet, but I know it’s scored, which is enough impetus for rectifying it.


Let’s get back to the original question (“what does one do away with when trying to eliminate all but the essential?”), and also to a related question, “what changes in that which is left when the superfluous has been removed?” Starting from the outside, one immediately notices that there is no separate case back; the watch is entered from the front, by prying off the friction-fit bezel/crystal assembly.






The bezel appears to have no allowance for gaskets, and it also seems like the crystal was originally glued in given the structure of the bezel. Because there is no gasket between the bezel and the case, the watch should definitely not be considered water resistant, which is normal for a dress watch, even more so an ultra-thin model. There is, however, a gasket mounted on the crown post, which seals the crown and tube area from dust at the very least.


Once the bezel is removed, one is greeted with the dial and hands, and no obvious way to remove the stem (most Seiko one-piece cases have a stem release near the crown, at the outside perimeter of the dial, so that the crown and stem can be removed from the movement, then allowing the movement to be freed from the case. Some have a two-piece stem instead, which is forcibly separated by pulling on the crown, or aligning the split in the stem such that the movement can fall out of the case when inverted). Typically, there has to be some external method of releasing the stem from the movement (or the crown and it’s portion of stem from the rest of the winding stem), as one cannot access the setting components to release the stem if the dial is still installed. Stick with me here. And most dials are held to the movement with screws that contact the dial feet from the edge of the movement, holding the dial tightly to the movement. Not so with the 6810-0080: because of the simplistic case design (to keep things thin), there is no external stem release. So, the dial and hands must be removed, to allow pressing on the set lever in such a way as to release the stem (there is a dimple in the set lever to facilitate this task and show where the pressure must be applied). How did the designers get past the usual problem of the dial foot screws not being accessible until after the movement is removed from the case? Simple- get rid of the dial foot screws! So while the dial has two feet, and the movement has two dial foot holes, there are no screws in place to hold the two together, the dial simply sits on top of the movement, and is loosey-goosey until the bezel is installed over it.
There is a friction spring (shown in the last photo above) pushing up from the underside of the movement casing ring, which keeps everything from rattling around when the case is completely assembled. That’s all fine and dandy for the watch owner, but it does present some additional issues for the watchmaker tasked with servicing, as each time the movement is accessed for anything such as a timing adjustment, the dial and hands must be removed. At least there are only two hands to reset afterwards, but the thin case does make their clearances very critical. I took my time with the casing procedure, and left the hands off until after I could do a cased timing analysis (a cased movement can show a different rate from an uncased one), so that in the end I didn’t have to re-enter the case a second time. Here is the movement once the dial and hands are off:



Please note most of these photos were taken before any cleaning. Here is the bridge side of the movement as received:



And with the bridges removed, you can see that the train is pretty compact in its layout and height, height clearances between wheels are noticeably less than with traditionally-dimensioned movements:



Let’s go back to that dial side shot of the movement though, notice the 4 flat jewels spread around the barrel arbor? Here they are from the bridge side, with the barrel removed and turned over:



The barrel does not possess a cover, so the mainspring is exposed on the lower side (towards the mainplate). The 4 jewels are placed to give a smooth surface of contact should the barrel or spring tilt some during winding or running. Also note that the 4 jewels are not included in the official jewel count- the 22 comes from the traditional 17 in a fully jeweled classically laid-out manual wind movement, plus 5 cap diafix cap jewels (for better lubrication retention and cleanliness) installed throughout the train. The omission of the barrel cover is done to save on thickness, which seems pretty clever as the thickness of a barrel cover would add at least 1-2 tenths of a millimeter thickness to the movement, or take it away from the thickness (and therefore strength and rigidity) of the bridges or mainplate.


Another area that this movement saves on height is in the escapement, namely with the pallet fork’s dog-leg bend which allows the teeth of the escape wheel to be on a lower plane than the roller jewel (these are the two parts that interact with the pallet fork jewels and jewel pin slot, respectively). It also allows the pallet bridge to sit a little lower, allowing more height for the balance wheel assembly itself. Here is the pallet fork:







Moving on, another space saving measure is found in the balance wheel. Here is the underside, showing poising cuts made at the time of manufacture- evidence that they did put some effort into adjusting this to positions:



But if you look more closely, you’ll see that the balance doesn’t have a normal roller table with a jewel pin installed on the balance staff under the balance arms, rather the jewel pin (aka roller jewel) is installed into the balance arms directly:



Now, I also notice that there appears to be a excess of neatly applied adhesive (remember, this is at over 45x magnification with a microscope- so that is in fact very neat application) around the hub of the balance staff, where it contacts the balance wheel. Considering the condition of the watch otherwise, I am not of the opinion that this is a hacky after-sales service repair. Rather, this may well be how the staffs for this caliber are attached at the factory. Given the roller’s position, frictioned into the balance wheel arm, this would not be an easy watch to re-staff, and due to the thin dimensions, the traditional method of riveting the staff to the balance arms could also prove difficult. I’d have to examine a few more examples before saying for sure, but at this point I suspect that the staffs are held in place by an adhesive, or at the very least helped by it. If you all wanted to donate your 6810’s to me, then we could find out for sure. Until then, it is only a hypothesis. In any case, it still seems to be holding fine, as this almost 40 year-old example is running very well after servicing. It cleaned up pretty well, too; here is a shot of the cleaned movement:




You can also see the stud carrier and regulator arms are set into the balance bridge pretty far, apologies that I don’t have a clearer picture of it. But it is almost like they float around a small hub of the balance bridge itself, instead of riding/sliding on top of balance bridge material as usual. This is thickness savings, but it seems to work just fine as the friction felt when adjusting them seemed comparable to normal designs, so I don’t think it would be any more prone to unwanted movement from shock than a thicker design.


So after going through this caliber, I see some good examples of why there reaches a point where you can’t just make a movement thinner by scaling every component down- there must be design changes throughout to ensure safe running for the long-term. Ultra-thin calibers live on the edge of “too thin”, and I see that Seiko has done a good job of riding on the safe side of that line, while still having very respectable “numbers” compared to other ultra-thin calibers.


Concerning numbers, the 6810 is listed here as being 1.90mm thick, which I take to be a measurement of the distance between somewhere on the top of the bridges and the bottom of the mainplate (so it does not include the height of the cannon pinion and hour wheel). The overall greatest height of the entire watch case (with the .8mm generic crystal which just sits proud of the bezel top, probably by less than .10mm) comes in at just under 4.40mm, by my measurements. The case is 32mm in diameter (side of case to tip of crown), so this wears like it isn’t even there, yet the design does not seem flimsy or fragile if I may editorialize, due to the solid lines and surfaces of the case and the seamless lugs- not separate but rather formed from the case frame itself by removing material in between to make room for the 16mm strap. I found an interesting quote from a Vacheron Constantin forum discussion, which can serve to put Seiko’s accomplishment with the 6810 into perspective:


There is no official definition or classification distinguishing thin calibres, each brand having its own terminology of extra/ultra thin/slim (no use of mega thin as of yet) but the industry more or less considers that a hand wound movement with less than a 3.5mm thickness can be considered ultra thin. According to Christian Selmoni the head of Product Development at Vacheron Constantin “a 3mm calibre is difficult to make but anything under 2mm – which functions – is a true feat which should be lauded.”

So in closing, here is what everyone else sees, otherwise hiding some pretty cool technology and skill:













Thanks for letting me share!
 

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I was wondering when you were going to share this one after you finally found it.
And to think you distracted me Wednesday with that 6218 Weekdater and forgot to mention you finished this one.
 

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Noah, thanks so much for sharing with us what we mere mortals can only drool dream about! :bravo_2:

That's an amazing movement and a great review! It's going to take a few re-reads just to absorb it all.

Great review! Great pictures! Amazing movement! :bravo_2: :bravo_2: :bravo_2:
 

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Beautifully written and photographed, even down to the 'Tokyo stripes'! A very clear and detailed explanation of a previously unknown calibre to me. Well done, Noah.
Loosey-goosey!!! :))
 

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This wonderfully written review of a magnificent caliber should be a sticky, what a post!


Congratulations on a extremely, very interesting read.


I salute you! :bravo_2:


PS I didn't know Seiko had such thin and elegant watches.
 

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Thanks for sharing, Noah. Great review and restoration. This 68 cal. must be the longest running SEIKO caliber in production?
 

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Great article Noah, and a very interesting read. The fact that these movements are still used is testament to the robustness of the design. The first side view of the cased watch made me 'wow'!


They say 'less is more' and this one proves that (and I don't just mean the price!)


Thank for taking the time to write this and post excellent pics, much appreciated.


Stephen
 

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Hi Noah,


Sometimes I get bored with the small talk here but then something like your review and technical enlightenment comes along :) . The side profile of the complete watch really hammers home just how thin the little joker is.


It is a looker too.
 

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Cracking effort there.

Amazing that superficially it just looks like quite a basic model yet scratch beneath the surface & it's a marvel. And the original price! Wow...
 

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Amazing . . . my head's spinning, I thought they just pounded them flat with a lump hammer . . . I'll have to come many times to re-read, thanks a lot Noah.
 

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Thanks for that Noah....nice way to start the weekend, a full cup of coffee and a well written analysis of a often overlooked caliber.
"...I placed a bid based on emotions, lacking common sense and decency..."
What a great line which I think most of us here could relate to.
The stem release situation was particularly interesting and I can't imagine how many hack watchmakers, when presented with this caliber went nuts trying to figure out how to properly uncase the watch and it would be interesting to see if it can be determined that adhesives actually were used by the factory to hold/help the staff. With all the things Seiko did to make the 6810 small, it's almost amazing that it ended up being a functional and reliable (?) movement. Neat stuff and I'm going to read it all one more time.
For fun, here's another old catalog shot from 1976:
 

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Noah, Thank You for your efforts put forth into your post :clap: As usual, A very detailed and superbly photographed addition to the Finest Watch Forum in The Universe :bravo_2: Simply the Best :) ;)
 

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What a great write up Noah, thanks for taking the (considerable) time to post this. I always thought it was strange that Seiko bought out Lassale - but not the movement rights. I wonder if they did, actually, secure some license from Piaget (or it's predecessor) to use the movements as a base to produce their ultra thin Seiko Lassale calibres??. I say this because, if you look at the architecture of the Piaget movements - there is a definite family resemblance, maybe somebody could try to do a cross ref on the movement parts, and see if there are any that can swap (unlikely I know). Here's a pic of a Piaget 40p - remarkably similar ,in my opinion.
 

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Really enjoyable Noah, i like how the barrel runs on those Jewels :clap: :clap: :clap:
 

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Thatnks for posting that, Noah. One of the calibres I've never had the pleasure of working on but hope to one day. Maybe not the skeletonised one in that link though - there's no metal left in those plates!
 
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