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Planning and lateral forethought in design are two elements present throughout much of Seiko’s wristwatch caliber production. If you aspire to make as many watches as Seiko does, you don’t get there by re-inventing the wheel for every caliber need. An example of this from the late 60’s is the 6139 automatic chronograph caliber, which was clearly based on the layout of the time and calendar-only 6106 and shared many major parts in common. This is smart engineering, because it also foresees after-sales service needs; stocking fewer parts to cover more calibers should be the aim of every manufacture, and Seiko does this well.
So does Seiko still practice this type of cross-pollination between calibers? A recent chance to service a newly acquired 6S78 Credor movement made it clear to me that this approach is still alive and well, between two streams of calibers we may not have suspected.
The 6S stream is a family of automatic and manual wind-only chronograph calibers, with various calendar/power reserve display options, and even a skeletonized version. See a nice table here, at watch-wiki.net: http://www.watch-wiki.net/index.php?title=Seiko_6S78
My example is inside a Credor Phoenix, a caliber 6S78 (automatic, date, no power reserve display). About a year ago, I had a conversation with a good friend and fellow collector about the basis of the 6S. Thinking about what little I knew of it [and a lot of that was from marketing material on Tag Heuer’s caliber 1887 ;-) ], I hypothesized that it could share a common ancestry with the 9S55, based on the location and design of the ratchet wheel, and the location and design of the pawl lever and transmission wheel next to it, under a sub-bridge. I couldn't see much else from photos so this was not exactly a lot to go on or enough to claim a clear connection, leaving me to keep my thoughts and suspicions to myself. At this point, I should also point out that the 9S and 8L streams are very much of the same lineage, with the apparent differences being the level of aesthetic finishing on the bridges and oscillating weight, and the adjustments made at the factory regarding time-keeping. There are more photos out there of 8L’s being disassembled than 9S’s, if you need to refresh yourself.
Well, flash-forward about a year to when this same collector I was conversing with earlier generously gave me an opportunity to acquire one of his 6S-watches, allowing me a great opportunity to find out where this caliber comes from, so to speak. Wanting to discover more, I did what any sane person would do- I took it apart!*
Below are several photos** that confirm to me the 6S chronograph is based on the 9S automatic caliber, which was also released in 1998 (coincidence? I think not!). While it lacks some of the surface finishing and painstaking adjustments and testing in 6 positions, it is still (in my opinion) as related to the 9S as the 8L is. So please enjoy, and if I somehow missed a meeting and everyone already knew this, still try to enjoy, and kindly point me to the previous discussion so that I can know once again I’m behind the curve- you won’t burst my balloon.
Take a deep breath, there’s a long way to getting back to this state:
The tool bit I made to remove the oscillating weight (the first movemenet part to be removed, otherwise no meaningful disassembly/servicing can be accomplished). I checked, but they didn't have any at the hardware store:
With the oscillating weight removed:
The dial side:
With the calendar plate and date dial removed. That large rocking bar mounted at 3 o'clock with 5 setting wheels beneath is pretty unique, and clearly shared by the 9S/8L. Same with the date jumper with integral spring tail:
Chronograph bridge removed:
Most of the chronograph parts removed. See the outside finger of the pawl lever laying on top of (disengaged with) the transmission wheel (at about 11:30 in the photo)?:
Underside of the train bridge, showing the pawl lever and permanently-mounted crown wheel:
Movement sans train bridge. Notice the silver-colored center wheel bridge- a unique design feature shared by the 9S where the center-mounted cannon pinion wheel rides on a post mounted to said bridge, such that the cannon pinion wheel’s teeth are on the bridge side of the mainplate, not the dial side as is tradition. I suspect the 9F might even do something similar, but that is a conversation for a different time! :
Showing the center wheel bridge flipped over, to see the post that the cannon pinion wheel rides upon:
Almost completely stripped! Notice the three tapped feet surrounding the balance jewel setting, at around 7:30 in the photo. We’ll talk about those later:
Barren dial side:
Now we’re getting into some shots taken during re-assembly. Here are the basic setting parts assembled, I suspect these are directly interchangeable with the 9S parts:
OK, remember those three threaded feet I mentioned? Here they are again, with the pallet fork installed where it is supposed to be, but with the pallet bridge a little…confused. Wrong feet, buddy!:
You see, the 9S, being a directly-driven center seconds caliber, has the train develop inwards from the balance, towards the center of the watch. The escape wheel is also moved over towards the middle of the mainplate, and the pallet fork accommodates this shift. So the mainplates are machined one way or the other, depending on which caliber is being produced. I suspect there was at least one sub-seconds caliber in the 9S/ 8L stream that would have used the layout that the 6S does. It is the 8L34 railroad pocket watch, with sub-seconds dial opposite the crown position, just like the continuously-running seconds hand is on the 6S stream. I liked seeing this type of flexibility being designed into the movement, and it further suggests that this whole family was developed concurrently. They clearly share several elements of design and layout, some that I noticed were the calendar and setting systems, the hand- and auto-winding systems, the basic train layout including the unique center bridge below (with obvious changes needing to be made to accommodate the sub-seconds at 9 and the chronograph complication), and the balance assembly and balance bridge shape/design (again with modifications to fit the chronograph parts above it).
I know of no other Seiko caliber streams that share these combinations of elements, suggesting that the 9S/8L/6S are uniquely and wonderfully linked.
Thanks for watching!
________________________
* Trained, experienced, and practicing watchmaker, do not attempt at home. Not having parts access for this caliber, I understood the risks involved with servicing it myself and was ready to send it to Seiko Japan if there were parts that needed to be replaced.
** Most photos were taken during disassembly, so remnants of the previous lubrication are still present, as well as possibly other pieces of debris that were later removed during the cleaning process. While that makes for a sometimes-messy photo, I have found it allows me to better concentrate on the re-assembly and oiling tasks.
So does Seiko still practice this type of cross-pollination between calibers? A recent chance to service a newly acquired 6S78 Credor movement made it clear to me that this approach is still alive and well, between two streams of calibers we may not have suspected.
The 6S stream is a family of automatic and manual wind-only chronograph calibers, with various calendar/power reserve display options, and even a skeletonized version. See a nice table here, at watch-wiki.net: http://www.watch-wiki.net/index.php?title=Seiko_6S78
My example is inside a Credor Phoenix, a caliber 6S78 (automatic, date, no power reserve display). About a year ago, I had a conversation with a good friend and fellow collector about the basis of the 6S. Thinking about what little I knew of it [and a lot of that was from marketing material on Tag Heuer’s caliber 1887 ;-) ], I hypothesized that it could share a common ancestry with the 9S55, based on the location and design of the ratchet wheel, and the location and design of the pawl lever and transmission wheel next to it, under a sub-bridge. I couldn't see much else from photos so this was not exactly a lot to go on or enough to claim a clear connection, leaving me to keep my thoughts and suspicions to myself. At this point, I should also point out that the 9S and 8L streams are very much of the same lineage, with the apparent differences being the level of aesthetic finishing on the bridges and oscillating weight, and the adjustments made at the factory regarding time-keeping. There are more photos out there of 8L’s being disassembled than 9S’s, if you need to refresh yourself.
Well, flash-forward about a year to when this same collector I was conversing with earlier generously gave me an opportunity to acquire one of his 6S-watches, allowing me a great opportunity to find out where this caliber comes from, so to speak. Wanting to discover more, I did what any sane person would do- I took it apart!*
Below are several photos** that confirm to me the 6S chronograph is based on the 9S automatic caliber, which was also released in 1998 (coincidence? I think not!). While it lacks some of the surface finishing and painstaking adjustments and testing in 6 positions, it is still (in my opinion) as related to the 9S as the 8L is. So please enjoy, and if I somehow missed a meeting and everyone already knew this, still try to enjoy, and kindly point me to the previous discussion so that I can know once again I’m behind the curve- you won’t burst my balloon.
Take a deep breath, there’s a long way to getting back to this state:
The tool bit I made to remove the oscillating weight (the first movemenet part to be removed, otherwise no meaningful disassembly/servicing can be accomplished). I checked, but they didn't have any at the hardware store:
With the oscillating weight removed:
The dial side:
With the calendar plate and date dial removed. That large rocking bar mounted at 3 o'clock with 5 setting wheels beneath is pretty unique, and clearly shared by the 9S/8L. Same with the date jumper with integral spring tail:
Chronograph bridge removed:
Most of the chronograph parts removed. See the outside finger of the pawl lever laying on top of (disengaged with) the transmission wheel (at about 11:30 in the photo)?:
Underside of the train bridge, showing the pawl lever and permanently-mounted crown wheel:
Movement sans train bridge. Notice the silver-colored center wheel bridge- a unique design feature shared by the 9S where the center-mounted cannon pinion wheel rides on a post mounted to said bridge, such that the cannon pinion wheel’s teeth are on the bridge side of the mainplate, not the dial side as is tradition. I suspect the 9F might even do something similar, but that is a conversation for a different time! :
Showing the center wheel bridge flipped over, to see the post that the cannon pinion wheel rides upon:
Almost completely stripped! Notice the three tapped feet surrounding the balance jewel setting, at around 7:30 in the photo. We’ll talk about those later:
Barren dial side:
Now we’re getting into some shots taken during re-assembly. Here are the basic setting parts assembled, I suspect these are directly interchangeable with the 9S parts:
OK, remember those three threaded feet I mentioned? Here they are again, with the pallet fork installed where it is supposed to be, but with the pallet bridge a little…confused. Wrong feet, buddy!:
You see, the 9S, being a directly-driven center seconds caliber, has the train develop inwards from the balance, towards the center of the watch. The escape wheel is also moved over towards the middle of the mainplate, and the pallet fork accommodates this shift. So the mainplates are machined one way or the other, depending on which caliber is being produced. I suspect there was at least one sub-seconds caliber in the 9S/ 8L stream that would have used the layout that the 6S does. It is the 8L34 railroad pocket watch, with sub-seconds dial opposite the crown position, just like the continuously-running seconds hand is on the 6S stream. I liked seeing this type of flexibility being designed into the movement, and it further suggests that this whole family was developed concurrently. They clearly share several elements of design and layout, some that I noticed were the calendar and setting systems, the hand- and auto-winding systems, the basic train layout including the unique center bridge below (with obvious changes needing to be made to accommodate the sub-seconds at 9 and the chronograph complication), and the balance assembly and balance bridge shape/design (again with modifications to fit the chronograph parts above it).
I know of no other Seiko caliber streams that share these combinations of elements, suggesting that the 9S/8L/6S are uniquely and wonderfully linked.
Thanks for watching!
________________________
* Trained, experienced, and practicing watchmaker, do not attempt at home. Not having parts access for this caliber, I understood the risks involved with servicing it myself and was ready to send it to Seiko Japan if there were parts that needed to be replaced.
** Most photos were taken during disassembly, so remnants of the previous lubrication are still present, as well as possibly other pieces of debris that were later removed during the cleaning process. While that makes for a sometimes-messy photo, I have found it allows me to better concentrate on the re-assembly and oiling tasks.
(imo).
