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Seiko 7S26 caliber - The father of 7S family of movements

March 13, 2019 7 min read 10 Comments

Seiko 7S26 caliber - The father of 7S family of movements

Many horology lovers still discuss which of the Seiko movements is the best. But that’s a broad question and, to answer it, one has to ask a lot of others. Plus, it really depends on personal preferences. First, you need to define the type of movement you prefer. Is it quartz, automatic? Perpetual calendar or chronograph?  Automatic or hand-winding? There are many factors that need to be considered. Plus, one needs to know a lot about watch movements. And, when it comes to Seiko, one has especially a lot to learn, because these people made a lot of great calibers.

Seiko caliber number

To prevent beginner’s mistakes, it is also important to know that the higher starting number of a caliber mark doesn’t necessarily mean a better caliber. That’s why we recommend learning more about each caliber individually, as all of them have their own virtues and flaws. For example, some calibers are famous for their power reserve, others for their accuracy, third for their durability etc. So, to answer the everlasting question, it is important to dig into details. That’s exactly why we started a series of posts that explore most famous watch movements around.

Seiko caliber 7S26

After our 6R15 study, today we’ll discuss the famous Seiko 7S26 caliber. It is said to be the top earner in the family of their watch movements and yet, it is considered as one of the low-end calibers. But this self-winding movement went on even further – it inspired a whole family of Seiko movements, called 7S movements, that all had great success. As some of you may probably know, the 7S family members are calibers 6R15, 4R35 and 4R36. But let us get to know their predecessor, the Seiko 7S26 caliber.


Year Introduced Movements Mainspring Hacking/Hand-winding
7S 1996 7S25, 7S26, 7S35, 7S36, 7S55 Traditional No
6R1X 2006 6R15, 6R20, 6R21, 6R24 Spron 510 Yes
4R1X 2008 4R15, 4R16 Spron 510 No
4R3X 2011 4R35, 4R36, 4R37, 4R38, 4R39 Traditional Yes

original from watch-wiki


Seiko 7S26 caliber is one of the automatic movements introduced in 1996. It is non-hacking and non-winding mechanism, with its accuracy ranging from -20 to +49 seconds per day. Equipped with 21 jewels, this fella works quite well with some of the great diver watches as it holds over 40 hours of power reserve, depending on the watch. For those less familiar with jewels function in wristwatches – they serve as bearings for the watch mechanism’s gears. Smoothened jewels are used because of their durability as a material and ability to minimize friction. However, a greater number of jewels doesn’t necessarily means that a watch is better or more expensive. The common number of jewels used in watch movements is between 17 and 21. Quartz watches may also contain jewels, but far fewer than mechanical watches, because they power on the battery.

Back to the father of 7S family, Seiko 7S26 operates at 21,600 beats per hour, which means it ticks 6 times in a second. That makes its second hand smoother than in quartz watches. Its operational temperature goes from -10 to astonishing +60 degrees Celsius (14-140 F). It also features Seiko’s Diashock system that makes him resistant to even severe shocks. All watches having 7S26 are thus quite robust to the external forces. The variants of 7S26 movement are 7S26A (1996), 7S26B (2006) and 7S26C (2011) with only small changes to the mechanism.


The caliber 7S26 was a part of some Seiko 5 entry level models, but mainly fills the bellies of SKX diver series and the older versions of Orange Monster (whose caliber was later upgraded to caliber NH35, just because 7S26 isn’t hackable and cannot be winded by hand – which are functions that remained quite popular to the broader masses, but we’ll discuss this later). That brings us to the fact of how 7S26 compares to other Seiko calibers. This caliber is often referred to as low-end caliber, as it is a work force of some lower entry watches, but in reality it is more of a power horse, judging by everything it can withstand. The best proof of that is the timepieces itself. Take a look.


When you start digging watches with Seiko’s 7S26 caliber in them, you almost get lost among the variants of diving watches, as the list isn’t short. However, SKX series is probably the most famous and we’ll mention only some of them. Most of these watches are keeping the classic diver look and are up to 200 m water resistant. What differs them are mostly details related to the case size, bezel of face color.


One of them, the SKX007 is probably the most common out there.

Seiko SKX007 Diver's 200m Automatic Watch, marked as SKX007  7S26 or simply Seiko SKX007 is one of the all-time famous diver watches. Launched in 1965, but then re-released in 1996 with the 7S26 inside, as the same caliber itself, it still remains one of the diving watches with the best value regarding its price out there. Regardless, it is a great competition for high-end timepieces, even today. The great thing is that you can fish one on Amazon for great bucks, going from around $200 and up. But make no mistake; the price is nowhere near its value. This simple timepiece is water resistant up to 200 m, as well the most of the watches of the SKX series. Experts would say it looks like a classic diving watch from the lineage: 6105-6306-6309-7002 because Seiko SKX series with 7S26 caliber inside is a direct successor of it. Plus, what keeps SKX007 still so appreciated is the fact that it is a highly durable timepiece. As well as its ancestors, it is made to withstand harsh conditions. Although the whole SKX line is pretty awesome, SKX007 has far best visibility, due to its minimalistic design, along with great chemical, magnetic and shock resistance. Plus, SKX007 has an ISO certificate for all these features, which makes it a seriously certified scuba diving watch due to the very strict standards these kinds of certificates have. No wonder it is often a favorite when it comes to Seiko’s diver series.


The internal mark on the case of SKX007 says: 7S26-0020, marking the caliber model and the dial design, as we previously said in our article about caliber 6R15. These are the same for its follower, Seiko SKX009 Diver's 200m Automatic Watch , which is different only by its bezel. SKX009 is popular for its so called Pepsi color scheme, because of its red and blue coloring of the bezel. So if you’re looking a diving watch that looks fancy and want to combine it with all the marine watch bands out there, this one will be a perfect fit. Prices on Amazon go from under $200 and up.


Seiko SKX013 Midsize Diver 200m Automatic Watch

For those interested in investigating further, Seiko SKX013 case mark: 7S26-0030 has a 5 mm smaller case diameter than SKX007. Its price is slightly higher just because it can be a rarer find, but it still stays in the lower range, between $220-$280 at Amazon.


Seiko Divers Automatic Mid-Size SKX023

Seiko Divers Automatic Mid-Size SKX023, case mark: 7S26-0050  is also definitely a good choice of a wristwatch with 7S26 caliber. It also holds a typical, minimalistic, diving design and has great visibility, but its case is even smaller than in previous models. What differentiates it further is that it is only up to 100 m water resistant. This means that it is not quite suitable for scuba diving, but rather swimming, surfing, snorkeling and shallow water sports. But it doesn’t prevent it from having fans, as it is quite hard to come across one for sale.


Seiko Automatic Diver' 200m SKXA65K Limited Edition (on Crafter Blue)

We also must mention one special edition, which is even rarer find than the previous model, but therefore quite interesting: Seiko Automatic Diver' 200m SKXA65K, case mark: 7S26-04N0, which is a Limited Edition to only 2999 pieces. It is specific because its bezel is also Pepsi-like, but rather split in half for red and half for blue color, unlike SKX009 that has only 1/3 of the bezel colored in red. Its price is, understandably, a bit higher, going from $500 and up.







Aside from these, we must mention the play of 7S26 caliber with so called Seiko’s Monster series of diving watches. Monster series look more robust by design than previously mentioned models, although they are also marked SKX, but since they have same caliber inside, they can handle pretty much the same abuse. The prices for these can also go well under $500, but well-kept models go even over $1000. The most famous are Black SKX779, with black dial and Orange Monster SKX781, with orange dial; both water resistant up to 200m. Keep in mind though that 7S26 movement is present only in early models.

To resume the story and compare Seiko’s 7S26 caliber, let’s first identify its flaws. The main thing that makes it a “low end” caliber is previously mentioned lack of winding and the impossibility of hacking. That may not sound as an issue for some, but it can be if it gets lazy and it is the main reason 7S26 is replaced with other movements. Some users on forums are reporting it slipping more than the average -20 to +49 seconds daily. In these cases, there’s no other solution than to take your watch to the service, but you’ll want to make sure that it’s certified. After all, 7S26 is a legacy caliber and if you’re a watch lover, you’d surely love to keep it alive and well as much as possible. But other than that, especially minding the price range of the watches 7S26 runs, the conclusion is that this is probably the best value movement you can get for the money. As for the looks, the fact that it runs mostly diver watches makes them easy to combine with literary all watch bands out there and they will still look cool. So, if you ask us, 7S26 is surely a movement to go for.


Shop Seiko Stainless Steel Replacement Watch Bands for SKX




Written by M.H. , Photo by Toni

Continue to read : Seiko Watch Movements Reviews

  • Part 1 - Seiko 4R35 movement
  • Part 2 - Seiko 4R36 movement
  • Part 3 - Seiko 6R15 movement
  • Part 4 - Seiko 6L35 movement
  • Part 5 - Seiko 7S26 movement
  • Part 6 - Seiko 8L35 movement
  • Part 7 - Seiko Automatic vs kinetic vs solar watches
  • Part 8 - Seiko Kinetic movement


External References:

10 Responses

Junaid Mogal
Junaid Mogal

March 11, 2024

Hello StrapCode,
I know this Article is almost 5 Years old but is there any other way I can contact you?

My query is what is Seikos most Accurate Automatic Movement?
Is it NH35? 7S26? 6R35? 4R35? Their latest 6R54?
I tried searching this all over the Internet but couldn’t find it anywhere, even in this article.

If you know about it please lemme know


March 04, 2021

@BernardSoliven, thanks 😊 we appreciate your feedback 👍💗

Bernard Soliven
Bernard Soliven

March 03, 2021

Great read. My father bought my first and only Seiko watch (7S26A) wayback June 18, 2005 – gift as college freshman. Still using it as I love its full neon luminous dial and hands – which is very hard to find these days. I recently took it to service (1st time) ‘cause it’s loosing charge – have it cleaned and lubed. Now it’s working fine, good as new – plus the scratches.

Michael Kornfeld
Michael Kornfeld

October 12, 2020

I have 23 jewels .

October 12, 2020

Hi John,
Thanks for the email and suggestion.
We will forward the watch model over to our design team to consider for future production. Please check in with us from time to time for updates.
We look forward to hearing from you again.
Please let us know if further assistance is needed.
Best Regards,
Strapcode team

John Ernest Chi
John Ernest Chi

September 30, 2020

You forgot the SKX031J, probably the rarest and most desirable SKX. Mine has the date in arabic. I have not seen another any where else.

Friedrich deHaan
Friedrich deHaan

April 17, 2020

Hi watch community folks !,

From 1980 up to 2016, I’ve pretty much hailed the 7S26 ánd then the 7S36 too, a lot even !
From 2016 up to this day, in 2020, I’ve hailed the NH35a ánd the NH37a, as much as I did
the previously two mentioned Seiko calibers.

Contemporary movements dó need the winding - and hacking-functionalities. These are the two most needed complications on ány watch, so that’s why the SII calibers need those upgradings. We live in the 21st century !

N.B. : no hard feelings, my dear Seiko-friends

Best regards,
Friedrich deHaan


April 16, 2020

Hello Cox,

Thanks for sharing your story with us and we hope you’ve enjoyed our article. We look forward to hear from you again!


April 08, 2020

In 1993 I bought an Allwyn wrist watch in India, a Seiko licence build. Day, date. The best watch I ever had. Still working! No maintenance at all. In the beginning I adjusted that watch. Approx. 20US$, if at all. Here my article: https://forums.watchuseek.com/f220/allwyn-watch-india-made-seiko-licence-build-1993-a-4922129.html

James Eagan
James Eagan

January 08, 2020

I have an old 007 that I’ve had for 12 years and which had never been serviced. I wore it regularly but it was awful with time – gained about 40 sec a day. Finally brought it in to a reputable shop that does their own work. They switched out the Malaysian-made 7S26 for a newer Japanese-made one. Took about five weeks to really settle in but it’s now gaining 7 sec a day. Gotta love that.

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