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

7 min read March 13, 2019

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 Seiko SKX diver watches

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.

Seiko mechanical movements - Seiko caliber 7S26 Review

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.

Seiko SKX007 & Seiko SKX009 on Super Oyster Stainless Steel Bracelets

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 Best Seiko SKX007 Bracelet - Retro Razor by STRAPCODE

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.

 The Best Seiko SKX013 Bracelet - Angus Jubilee by STRAPCODE

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.

 The Best Seiko SKX023 replacement bands by STRAPCODE

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.

Crafter Blue Curved Lug Watch Band for Seiko SKX007

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 any bracelet out there and they will still look cool. So, if you ask us, 7S26 is surely a movement to go for.

 Strapcode SKX007 stainless steel bracelet-full collection

Shop Seiko Stainless Steel Replacement Watch Bracelets for SKX




Written by M.H. , Photo by Toni

Continue to read : Seiko Mechanical Watch Movements Reviews

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


External References:

10 Responses

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.


November 27, 2019

great read, I have a 1996 purchased SKX175. (7S26-0020) and never have gotten a definitive answer on how it differs from the SKX009.
worn this watch since new and had it “serviced” with seals changed and watch lubed by a local guy (now gone) a couple of times
and now it’s losing 2-3 minutes a day. Seiko gives no details on their service, just send it and a price. after owning this watch for nearly 25 years I’d like more control over what happens to it. BTW, what is the difference between a 175 and a 009? thanks!

Sergio Montenegro
Sergio Montenegro

November 27, 2019

Hece unos meses adquirí relojes seiko con calibres 4r36 y otro con 7s26 y la las desviaciones de segundos diarias de 6 a 10 son casi iguales. Gracias por la oportunidad de opinar.


July 11, 2019

Hello Mihai,

Thanks for the response and for taking time to read our article. We have been trying to acquire the information and clarifications from Seiko US. Unfortunately, we have not heard back from them. Anyhow, thank you for the clarification and letting know the differences with 23 vs 24 jewels…Thanks for the continuous support..We look forward to hear from you again.
Please feel free to let us know if you need any further assist.

Best Regards,
Strapcode team, Sam


July 04, 2019

Hello Hilary,
Seiko was actually my first watch I even owned. It was passed down from my dad.. A 150m quartz diver that looks identical to the SKX007, and it was his first divers watch as a fire fighter. With regards to your mom, we’re sorry for your lost…our condolences
to you and your family….
Please feel free to let us know if you need any further assist.

Best Regards,
Strapcode team, Sam

Hilary Wons
Hilary Wons

June 12, 2019

Seiko was one of my first watch that I ever owned. It was for my graduation gift from my mom but she passed 6 months before mom could give it to me.


July 04, 2019

Great article. Regarding the mainspring, the 4R3x and 7S also have Spron, just not the 510. I believe it is 500 but I’m not sure. The most important difference for long-term reliability between these movements is that the all the 4R36, the 4R35 starting with the B version (24 vs23 jewels) and the new 6R15D 24 jewels (not the 23 jewels) have a jewel on the underside of the mainspring arbor and bushing on the top. This greatly increase the longevity of these movements compared to the 7S and older 6R and 4R1x which were basically metal on metal and developed wear in time leading to instability in power delivery. This creates a weird situation in which a 4R35B or 4R36 can be much more durable and stable compared to a higher end 6R15 – 23 jewel version.

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