The “new” Seiko 6L35 caliber introduced in the Presage SJE073J1/SARA015, or is it?

So at Baselworld 2018, Seiko introduced a new Presage model. The international model name is SJE073J1. There was a fair bit of fanfare to this model because of the “new” caliber 6L35 that powers it. It promises to be slimmer (3.7mm), running at a higher 28,800 bph and has a fairly large power reserve at 50 hours. This is in comparison to the 6R15 movement that it’s kind of replacing, which runs at 21,600 bph, has a power reserve at 50 hours but is fairly thick at 5.3mm.

6L35+Movement full

The new 6L35 is also factory adjusted to +15 sec / -10 sec a day versus the +25/-15 sec a day of the 6R15.

new caliber statement

All in, this seems like a great move by Seiko, except that the Presage is now JPY 240,000 or USD 2,200!

You can see the official Japanese website Basel 2018 announcement here and the English press release here.

I’m fine with all these except for 1 thing, this is not a completely new caliber from Seiko Japan. In fact, it was first introduced way back in 2007 as the 4L25 and was finally discontinued in 2013 as the 4L75, before being resurrected in 2018 here as the 6L35.

The 4L25 and 4L75 movements are hi-beat movements, beating at 28,800 bph and had a power reserve of 42 hours and 50 hours respectively. However both 4L movements only had 25 jewels, 1 less than the 6L35. At the point of introduction, they were one of Seiko’s slimmest automatic movements at 3.6mm thick and measured 25.6mm across. These measurements were by the way also shared by the ETA 2892 and this was no coincidence as Seiko meant for the 4L caliber to be a drop-in replacement for the 2892.

Other than having the same dimensions and movement specifications, Seiko also took the liberty to utilise several Swiss designs in the movement architecture, thus moving away from several design quirks that would have identified it as a Seiko movement. For example, the 4L utilised the reverser wheel design rather than Seiko’s magic lever to wind the mainspring, and also adopted the Incabloc anti-shock suystem rather than its own Diafix antishock system. As others before me have speculated, perhaps this was all done in the hope of attracting Swiss customers.

Also it’ll be interesting to note that even Seiko’s highest end movement in the Grand Seiko 9S (9S6X and beyond, as the 9S5X uses the magic lever) uses the reverser wheel design and not Seiko’s magic lever system.

Not surprising, Seiko did succeed to some extent in this as it was thought that Soprod eventually licensed this design from Seiko and produced the Soprod A-10 caliber from this base caliber. Note that neither company have ever acknowledge who really designed the movement and who licensed it.

Soprod A10 image from Watchbase

The 4L25 movement was introduced by Seiko in 2007 in the SARA 001/3/7/9/11/13 models. At that time, the models were incredibly expensive at JPY 189,000 and did not sell well. They were discontinued in 2008.

SARA001 3 GROUP photo

SARA001 (top) and SARA003 (bottom)

all sara.JPG

SARA001/003/005/007/009/011/013 in all their splendor

sara001 4L25 caseback

The 4L75 movements were introduced by Seiko under the Credor lineage under the GCBW 993/5/7/9 and sold for JPY 260,000 between 2007 and 2013. (Side note: Compare the price of the Presage now against the Credor prices then).



How did I come to the conclusion that the new 6L35 was derived from the old 4L25/75 movements?

  1. The JDM model number of the Presage is SARA015. This was the first important clue that I got. The previous SARA series that was discontinued in 2008 ended with the model number SARA013. Hence it made sense for the new model using the same movement to be numbered in order (i.e. 15 follows from 13. Seiko do not usually use even numbers in its naming system except for special models). This cannot be told from the international model number which was SJE073J1. I have to give credit to akable at plus9time for this fact, as he was the only blogger I’ve seen so far to quote the JDM model number alongside its international model number.SARA015 pricing.JPG
  2. Once I’ve gotten the JDM number, I could then compare the dimensions of the old 4L vs the new 6L. The thickness, diameter, power reserve, beat rates were all a match!
  3. I then compared pictures of the new 6L35 versus the 4L25 movements. It was oddly difficult to find ANY real life picture of the 6L35 on the Internet and I had to rely on the press image.
comparison with comments.jpg

Comparison between 4L25 and 6L35

The green boxes illustrate what are the smoking guns that they are the same movement.

a) The fine adjuster design looks to be unchanged.

b) The same 3 screw design on the rotor remains unchanged.

c) The slightly oval shaped cut out where the balance bridge meets the main bridge remains unchanged.

The red boxes highlights where the important differences are

i) The balance wheel has a different design now. Previously, the 4L had a smooth balance wheel, while the 6L now has studs on the circumference

(Edited: There is no difference in the balance wheel used. 6L is still using the smooth balance wheel, but now the studs are gold, compared to the silver studs used in the 4L)

ii) More importantly, the anti-shock system is now conformed to Seiko’s flower-shaped antishock, and no longer uses the Incabloc antishock. This also brings it in line with the so-called higher end Seikos (i.e. 9S/9R/8L/4S), which uses the flower shaped anti-shock versus the tadpole/rectangular shaped anti-shock used in the lower end Seikos (i.e. 7S/4R/6R/8R).

The 6L35 appears to be a mix of the 4L25 and 4L75 as it has the power reserve of the 4L25 (45 hours), but the accuracy of the 4L75 (+15/-10 sec) rather than the 4L25 which was slightly less well adjusted. This helps to explain the rather high pricing of this Presage which really is more in line with the pricing of the Credors powered previously by the 4L75.

Why then did Seiko make an imperfect clone of the 4L given that all the fundamental specifications of the movement are the same? I suspect that this was due to the licencing arrangement between Soprod and Seiko regarding the 4L and Seiko had to work around this by changing, cosmetically, certain parts of the 6L including the balance wheel and anti-shock system in order to avoid infringing their agreement with Soprod.

This then brings us to the next question of why Seiko had to bring back the 4L caliber to power its new Presage models.

Firstly, as many people have correctly noted, Seiko movements are generally never thin. For example, all modern GS are at least 13mm thick. Having the 3.6mm thick 6L movement would allow Seiko to introduce true thin dress watches below 10mm and better compete with its European counterparts.

Secondly and more importantly, Seiko likely made a huge expense in designing and manufacturing the 4L family, and it was only used in models from 2007 – 2008, with it then being relegated to the Credors until 2013. Seiko probably had to recoup the capital it invested in building the machines to manufacture the 4L family, and was waiting for the right opportunity to utilise the 4L movements in watches that could fetch a higher price. After all, it’s pretty telling that the 4L/6L is the first ever movement that went from an upper tier line (Credor) to a lower tier line (Presage). Every other movement generally stayed within its own price bucket/line, with the exception of the Seiko 4S, which moved upward to power the Credor from its pedestrian origins powering the normal Seiko mechanical timepieces.

The time is now right for Seiko to introduce ever higher priced watches that do not carry the GS designation which requires manpower intensive work in adjusting and then certifying each and every watch. By introducing the 6L powered Presage (probably the most expensive time only Presage ever), Seiko could hope to recover some of the investment made in its movement, while getting consumers used to ever higher price points in the Presage range. This would then allow Seiko to creep the price points of its top tier Credor and Grand Seiko lines upwards as well.

(Side Note @ 4 April 2018: It was brought to my attention below by akable that if the 6L was really a close clone of the 4L, then it will no longer qualify for the “Trimatic” branding that Seiko had associated with the Presage line as it will no longer be using the magic lever winding system.

The “Trimatic” line refers to the usage of Seiko’s magic lever winding mechanism, Diashock anti-shock system and proprietary SPRON alloy used to manufacture the mainspring and balance spring. See here for an explanation.

I went to the Seiko Japan Presage website today and I did not find any mention of the “Trimatic” term any longer. Perhaps it is no longer in use.

We will know for sure if the 6L is indeed “Trimatic” once real life photos of the movement surface.)

7 thoughts on “The “new” Seiko 6L35 caliber introduced in the Presage SJE073J1/SARA015, or is it?

  1. Pingback: Origins of the Soprod A10 – ultracrepidarian

  2. Interesting comparison and there does likely seem to be a connection to the 4L series.

    I have just a couple of comments, the 6L35 is specified with a 45 hour power reserve and not 50. The 4L75 had a power reserve of 42 hours and not 50, so they are quite close and the improvement could be from improved materials. Also the 4L75 was a 25 jewel movement not 26, so there is some change in the 6L35.

    The general movement design between the 4L and 6L does look very similar with the bridge design and even the rotor mechanism. If the 6L35 uses the reverser wheel design and not Seiko’s magic lever system, they will not be able to use the Trimatic branding that has been commonly seen on current Presage branding.

    • Nice to see you here. I’ve corrected my mistake as we spoke about the power reserve of the 6L35. You’re also right about the jewel count of the 4L75, which I’ve verified through Google image search in the 4L75. I’ve placed probably too much reliance on watch wiki’s information in the 4L75.

      I’ve not been able to verify the hour reserve independently though. Do you have a reference site I can point to?

      I was not aware of this Trimatic branding but I’ll do some research and update my article accordingly.


      • Sorry about the errors on Watch Wiki! That’s my work. I got it from the manuals at the time, but now I see that the actual released 4L75 watches say “25 jewels” and “42 hours”. Thanks Anthony!
        As for the 6L35, it’s a really interesting development. I’d say that the Soprod was derailed by their acquisition and Seiko decided to restart production.

  3. Thanks for this excellent blog post. I bought one of the SJE073 watches from an authorized dealer in the US. The first one was defective out of the box, the movement would hack when the crown was in the date set position; the AD replaced it quickly. I received my 2nd unit last week (week of 2/10/2019)

    I did some testing of the 1st watch to see how much time it lost/gained in different positions. I first fully wound the watch (Seiko says 20 turns is full wind, I did 30 to be safe), set the time to then let it sit in each position for 24 hrs. I noticed the watch would swing from time lost to time gain within the first 3 hrs. of testing, or swing from virtually no time gained/lost in the first 3 hrs. to time gain. Over the next 21 hrs. the watch would increase it rate (I checked it every 3-4 hrs.). Nothing was out of the Seiko spec of +15/-10 sec. per day. I found similar behavior in the replacement unit so it wasn’t an anomaly I observed with the 1st (defective) watch.

    I have a few Swiss mechanicals (ETA 2824-2, 2892, Selitta SW200-2). None of them exhibit this kind of isochronism within the first 24 hrs. from full wind. Since this watch cost as much if not more (3x more than my Selitta equipped watch) I expected similar behavior. This movement doesn’t exhibit as consistent time keeping based on the state of mainspring’s wind compared to my Swiss watches, not even my Speedmaster manual wind with the 1861 movement (which does exhibit isochronism in the last 12 hrs. before it goes dead but I expected that in such an ancient design).

    Either Seiko doesn’t adjust these movements as well as it’s Swiss competition or there’s something in the design that causes this variation. If Seiko wants to play in the US$1000+ space they better up their game. From what I can tell this Seiko movement ain’t even the equal of a very old ETA (or Selitta) design that goes in watches charging often less than half the price.

  4. I recently bought the SARA015 in Japan and I am wearing it for 5 weeks now.
    The accuracy is at approx. +4 sec./day. Not bad at all and en par with ETA’s 2892-A2.
    I am really excited to see more watches by Seiko using the new caliber.
    Let’s see what they will show at this year’s Baselworld!
    If the price is lower than the limited 2018 edition, it really can compete with Swiss’ ETA-calibers.

  5. A few minor updates:

    The Seiko SARA line with Cal. 4L25 (SARA001/3/5) appear in the 2006 edition of the Seiko international catalog, moving their introduction up one year. SARA007/9/11/13 appear in 2007. They also appear on the website that year according to SARA001 is gone after September 2007, SARA003/5/7/9 last through April 2008, and SARA011/13 are gone after October.

    Credor introduced Cal. 4L75 in the Signo GCBW999/97 (they count models backwards!) in 2007, and introduced the Signo GCBW995/93 and Node GCBW991/89 in 2008. The later Signos were retired after 2011, leaving only GCBW999 and the Node models in 2012. Node GCBW989 was the last retired in 2013.

    It’s interesting that Seiko has not used Cal. 6L35 again since that one 2018 Presage model, or at least not that I’ve seen!

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