The little known Seiko 7s55 caliber


When it comes to Seiko’s entry level automatic movements, most people will readily think of the well-liked and reliable 7s-caliber automatics that are found in the garden variety SKX and limited edition SKZ divers and of course, the popular Seiko 5 family of affordable watches.

The 7s26 is perhaps the most widely known movement in the 7s-family and is extensively used in the base line Seiko 5 model. The Seiko 5 Sports and Seiko 5 Superiors are adorned with the slightly upmarket 7s36 movement, which has 23 jewels – two more jewels than what the 7s26 has. Limited production run 7s-caliber divers such as the SKZ203K Yellow Monster and the SKZ201K Seiko 5 40th Anniversary diver’s watches also use the 7s36.

So what’s interesting about the 7s55?

The 7s55 appeared towards the later part of the 1990s and it was the shortest-lived member of the 7s family.

In essence, the 7s55 is mechanically similar to the date-only, 23-jeweled 7s35 caliber but fitted with a decorative “Tokyo Stripes" oscillating rotor with red inscription for aesthetic purposes. As with the other 7s family calibers, the 7s55 is a fully automatic movement, with no auxiliary hand winding or hacking feature and runs at the standard 21,600 beats per hour.

Unfortunately little is known about the history of the 7s55 movement as not many of them were made, compared to the mass produced 7s36. The bulk of 7s-caliber movements, prior to the end of  2006 were manufactured by the Seiko Instruments factory in, Singapore.



7s55A movement 7s36A movement

Above: Comparison of the 7s55 (left) with the plain looking 7s36 (right). Borrowed images.


The 7s55 was never used in any other Seiko model and it wouldn’t have made sense for a decorated movement like that to be used in a solid caseback diver’s watch, where it cannot be seen.



Models that used the 7s55 caliber 

The 7s55 debuted in a select range of Seiko 5 Superiors, which I call the “SLX-series" from their model reference numbers. All other Seiko 5 Superiors used the cheaper 7s36 day/date movement.

Only six variants were made: the SLX001K, 003K, 004K, 009K, 011K and 012K in stainless steel and gold tone guises with glass display backs to showcase its lovely rotor.




Above: SLX001K, SLX003K and SLX004K (top row). SLX009K, SLX011K and SLX012K (bottom row)



The SLX-series Superiors were cased at Seiko’s overseas production facility in Hong Kong while the  movements were specially assembled in Japan. They were made available in small quantities to the Southeast Asian market. Contrary to what some have to be led to believe, these models were not exclusive to Japan although some Japanese collectors managed to get hold of the 7s55 Superiors.

The SLX-series Superiors were divided into two distinct designs: one with a subtle polygonal bezel edges, a date magnifier, Dauphin-styled hands, a larger crown and a plain stainless steel bracelet. The other design lacks a date magnifier but has a softly serrated bezel and baton-like hands. Both designs came in silver, black and silver dial with gold accents.

An unusual trait in the SLX Superiors is that they had regular bracelets which allows fitting of aftermarket leather straps. Seiko 5 Superiors made in 2003 onwards tended to have integrated bracelets, which I don’t really prefer.

The SLX-series Superiors were a hit with Seiko collectors and they were snapped up quickly. Due to its scarcity, the SLX Seiko 5 Superiors have earned its title as a collector’s item. A popular watch forum website in Thailand, Siam Naliga succeeded in getting their Seiko to issue them with a customized, Siam Naliga official watch based on the black dialed SLX003K.

Made only to a mere 200 pieces and individually numbered, this limited edition SLX003K ensured a place in the Seiko Collectors’ Hall of Fame.



Siam Naliga SLX003K 200 pieces meant exclusivity and collectibility

7s5503 Caseback

Above: Photos of the elegant Siam Naliga SLX003K watch. Note the inscription on the dial. Images from Siam Naliga.


I’ve never really given thought to buying a Seiko 5 Superior but if I absolutely must have one, the black SLX003K would definitely be my choice! 🙂



Will Seiko reintroduce the 7s55 in the future?

That would certainly be wishful thinking! Many years had passed since the 7s55 was discontinued and Seiko made no attempts to release additional models using this caliber. I don’t know why the Japanese watch company pulled out the 7s55 from production in a very short span of time, but I guess the movement was more expensive to make compared to the more common 7s26 and 7s36.

I doubt very much that Seiko will reintroduce the 7s55 caliber as they already have rolled out their recent 4R15 movement, which debuted in their SRP-series mid-priced automatics in 2008.

There’s not much point in the 7s55 caliber making a comeback. For one thing, from the marketing perspective, the 4R caliber fits in between the flagship of the 7s-caliber family – the 7s36 and the more upmarket 6R15 movement, found in higher priced Seiko Premier, Spirit and Alpinist ranges. Having too many calibers in the entry level segment would confuse consumers and 

For another, the reintroduction of the 7s55 movement would probably compete with Seiko’s 4R15 caliber. Seiko could have reissued the 7s55 long ago if they wanted to but they didn’t. I guess it wasn’t feasible for them to do so for marketing and cost reasons.



Movement Versions Where assembled Calendar Beats/hour Jewels Models used
7s26 A, B Singapore, Malaysia, Japan Day/date 21,600 21 Seiko 5, SKX divers,
7s25 A Japan Date 21,600 21 SBDA-series Ti Samurai divers
7s36 A, B Singapore, Malaysia, Japan Day/date 21,600 23 Seiko 5 Sports, Seiko 5 Superior, SKZ divers, JDM Monster divers
7s35 A Singapore, Malaysia Date 21,600 23 SNM-series automatics and divers
7s55 A Japan Date 21,600 23 SLX-series Seiko 5 Superiors


 Above: Table showing the entire 7s caliber family and its attributes


The movement table above summarizes the features of the 7s caliber family. The 7s26 and 7s36 continues to power the Seiko 5 family of watches and 7s-caliber divers today. The date-only 7s35 debuted with the SNM001K, Seiko’s first automatic dress watch that didn’t belong to the Seiko 5 family. It is also used in the SNM-series divers such as the stainless steel Samurai divers and the North American “Landmonster" 200m divers.

Oddly enough, Seiko opted for the 7s25 instead of the 7s35 for its highly regarded but discontinued Ti Samurais. The 7s25 was not fitted to other models other than the SBDA-series Samurai divers. At the time of writing, it’s not known whether Seiko will reuse the 7s25 in their future models.


More pictures of the SLX-series Superiors

Here are some additional photos of the 7s55 Seiko 5 Superiors for your viewing pleasure. All photos depicted belong to their respective copyright holders.

As you can see, much attention has been given in the fitment and finishing of the SLX Superiors. The solid linked bracelet is top notch and resembles the upmarket kind used in some Japan market Prospex and Brightz models.

It’s a shame that Seiko decided to stop production of these fine looking Seiko 5 Superiors as I would have bought one if I had the chance years ago. Unfortunately for die hard enthusiasts, Seiko runs a business to make profits and to please their shareholders, not to please Seiko WIS folks.

The SLX Superior is one of the examples of highly desirable models that appealed to a select few of discerning Seiko watch lovers, not the masses. Models that don’t have high global demand are likely to be discontinued as the company sees it fit. Now you know why the evergreen SKX007K  diver is still made to this day, despite being introduced way back in 1996!

Present owners are likely to hold on to their prized 7s55 Superiors as they recognize the high collectability status of these timepieces.



SLX009K SLX003K SLX001K 7s552pb

SLX009K on leather strap SLX011K on leather strap

Top: Selected models of the SLX-series Superiors. Images belong to their respective owners.

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Hi Quartzimodo,
Thanks for your well-written and detailed article. It’s amazing that you have been able to provide so much on this movement that is so-called, rare. In fact, this is the first time I hear about it! Hehee!
I have always enjoyed reading your articles as there is so much one could learn just from reading them.
Well done and keep your articles rolling in! 🙂
Thanks and Cheers,

Hi Roy,

Thanks for the compliments. The 7s55 is one of the Seiko calibers that many people outside the WIS circle don’t know about and I thought it would be an interesting topic to write. If you can find one, grab it before someone else does! 😉


Dear Quartzimodo:

I really enjoyed reading this article and it successfully addressed most of the questions I had regarding the Seiko caliber 7S55. I have never seen one in the flesh, and doubt I ever will, given their low production numbers and scarce availability. Perhaps these were the finest Seiko 5’s ever made. I’ll be honest and say that the current crop of Seiko 5 labeled watches don’t do much for me.

Now onto the 7S55. I think the main attraction of this movement is its 100% Japanese manufacturing, nice finishing and overall rarity. However, having said that, I have become a huge fan of the new Seiko 4R calibers, more specifically, the 4R16A day/date movement offered in some SRP and \Superior\ series of Seiko mechanicals. I think the 4R likely is the \spiritual\ successor of the 7S55. I find the finishing of this movement to be top notch and enjoy its 50+ hour power reserve plus better accuracy (in my view) vs the older 7S family of movements. The quickset change function for the day/date feels very solid, refined and reassuring. Even the sweeping action of the seconds hand seems smoother with less \stuttering\ than in the 7S26 watches. Cases and bracelets in the SRP’s seem to be a grade or two above in quality and finish as well.

I recently purchased a Seiko SRP013K1, with the cream colored dial, military numbers and brown calf strap. While this particular model did not set the world on fire when they were first introduced back in 2008, I find the watch to be quite enjoyable to wear and own. The accuracy beats past 7S26 based watches right out of the water. I have handled other 4R15 (date only) and 4R16 samples and the watches are really nice for being entry level mechanicals. Too bad, hacking and hand winding are still absent, but Seiko’s marketing wants you to spend a few hundred more for a JDM 6R15 mechanical timepiece.

My only question at this point would be…. Where is the 4R15/4R16 being manufactured at? Since the rotors in these watches do not have the \Japan\ printed as country of origin, my best guess is that the 4Rs are being made in Singapore along with the watches of the SRP and \Superior\ series. Maybe you can clarify a bit on that regard.

Hi Frank,

Glad you enjoyed the article. It’s probable that Seiko tested out the market with the 7s55 but its relatively high asking price led to dismal worldwide sales, so they discontinued it. Their extremely rare status makes the SLX-series Superiors worth the price of admission. Die hard Seiko collectors who knew about the 7s55 back then wasted no time in getting one.

There were divided opinions whether the 4R-caliber is closer towards the 6R15 or the 7s35/36. My opinion is that it’s a stripped version of the 6R15 as the 4R15/16 movement is slightly larger than any of the 7s-calibers – and also the fact that it has a bigger mainspring. With 50 hrs worth of reserve and a decorated rotor, its characteristics are closer to the 6R15B.

Where are the 4R calibers made? Not sure at this point, it could be either Singapore or Malaysia. AFAIK since late 2006 all 7s movements made outside of Japan are assembled in Malaysia. It’s possible that all entry level automatic movements, including the 4R15/16 are also made by Seiko Epson’s plant in Malaysia.

BTW, I don’t think the “Superior” name is officially used with certain 4R16 models, unless there is documented evidence that they are called “Superiors”. The name “Superior” has always been associated with the Seiko 5 family and the SRP-series models are NOT part of Seiko 5 Superiors.


Hello Quartzimodo,

Another exceptional article on a very obscure & hardly known Seiko watch model & movement.
Seems that the superior had a retail shelf-life that was gone rather quickly, and no doubt for good reasons as you mention.

I would think that the Market for these limited production runs such as the yellow/blue and red dialed monsters should also have a large popularity in Malaysia, but it seems like over the years that the Thailand market and the people there adore Seiko with great ferver, and hence the special make-ups and limited editions made for & distributed for that market.

Well I’m sure the future offerings from Seiko in the 4, 6 and 7 series will forever keep us on our toes, and even more so keep us thrilled with the upper level offerings as displayed by the recent release of the Ananta line. Ummm, there’s much to drool about there in the Ananta series I think especially with what new releases they will unwrap as time goes by. (May a diver be released in the Ananta line sometime soon? One can only hope!)

Great article Zami as usual, and I’m glad I caught this one!


Hi Jimmy,

Thank you for your comments, sir. Yellow, red, blue and green Monsters are never officially sold in Malaysia. These are special models for the Thailand market. I have not seen any of them for sale here. Word has it that Seiko Japan will be discontinuing the Seiko 5 series altogether. Which means that the cheapest Seikos would be the 7s36 equipped Seiko “Superiors” (not to be confused with the Seiko 5 Superior).

With Seiko going upmarket, they’re forcing loyal consumers to spend more on higher priced automatic models. You can see the emerging patterns – the lovable SBBN007 discontinued and re-marketed as the insanely expensive SBBN015 and 017. The discontinuation of the SKX031K Submariner and its siblings.

Maybe someone in the marketing department convinced Seiko’s board of directors to dispense with Seiko being a “cheap-but-reliable” watch brand. They’re going head-to-head with the Swiss watch industry on this one. And if Seiko releases a diver from the Ananta line, you can bet very few can afford one.



Great article man.

I do enjoyed reading your blog. I’m a watch maniac too. Seiko had so many range of models that suits everybody. Starting from a basic line of model until the very complicated one. What I liked about Seiko is, they offered a good quality watches with a affordable price. Most average guy like me can buy it & enjoy a good timepiece.

I’m still new in watches & also had my own blog. But in Malay language. Still new & still need to improve myself. Here’s mine


Hi DJ,

Your blog is probably the most prolific watch blog in Malay. However from my observation, non-English blogs are restricted to readers who understand the native language. Therefore your blog won’t be likely to pull in international visitor traffic. BTW, I noticed that Malays often refer to movements as “engines”, which is a totally incorrect terminology. Even in English language, watch movements have never been called “engines”.

Perhaps you’d want to educate your peers to use the English term “movement” instead, or the literal translation “pergerakan”. BTW, congrats on owning the SBDC001 diver and the SNM011K S/S Samurai! They’re both two of my favorite divers. See if you can score on a SBDA005 orange Ti Samurai! 😉


Thanks man. I should changed the terminology. Hehe…

I just made it Malay because at the moment no Malaysian watch blog give information in Malay. Your blog is very informative & you are very knowledgeable. Keep up the good work man

hi guys im new to this blog thing, but i just wanted to say that i have had many automatic watches ranging from tag to rolex.i have recently bought my first seiko landmonster and i just cant get over how percise the movement out does my rolex deep sea at a fraction of the cost…wow for seiko…thanks larry

That was a really interesting post, I enjoyed reading it. You are dead right!

My cousin recommended this blog and she was totally right keep up the fantastic work!

A peculiar thing about these Seiko 5 models is that they have only 4 features since the day is missing. Seiko 5 was supposed to stand for the most 5 basic features in a watch (Seiko`s view). Would have been nice to see the 5 replaced by a 4 in the shield.

Thank you for such interesting post on SLX-003K. This is my first Seiko Automatic wrist watch. Of course, in the watch shop in 2001, it was, by far, distinguished from other Seiko 5s. Unfortunately the crystal is not made from sapphire mineral and the case is quite easy to scratch. However, it is still a good-looking watch with precise movement that I use for daily work.

Hi Micheal A.,

Great to know that you happen to own one of the rare 7s55 Seiko 5 Superior models. 🙂

AFAIK, very few Seiko 5 Superior models are fitted with sapphire glass. There are Seiko dress watches that are fitted with sapphire crystals that are of the “generic” type, i.e., not belonging to any particular sub-range of line of models. Such Seiko watches usually have the text “SAPPHIRE” printed onto their dials as its main feature.

As for the brushed stainless steel case, I noted that none of my Seiko watches are impervious to light scuffs and scratches. Fortunately in most cases light and medium deep scratches can be buffed out with jewelry polishing paste or an abrasive toothpaste with and old toothbrush plus a 3M scouring sponge. 🙂


Thank you for your insight. I bought some polish paste to take care of the SLX003K. Since you said that it is a very rare piece of mechanic, so I put it aside and only wear it on a special occasion. I bought another Seiko watch, now with sapphire crystal and manual winding. It has 6R15B movement, and also very good looking. I don’t remember the name of its series ,maybe SARB series with white dial and silver numbers but someone call it “Grand Seiko for poor man”. I also have a very much pleasure to see it every time. Again, this series is disappeared already.

Do you know how much value now the seiko superior 7s55-0010?

Do you know how much value now the seiko superior 7s55-0010?appreciate your answer.

Hi Ramon,

I really wouldn’t know what it should be worth, but I found an ad for an SLX001K with an asking price of Rp 950,000 (Indonesian Rupiah). That translates to about US$68. Is a 7s55 powered Seiko Superior rare? Yes it is. Is it that valuable? Not really. As you have already read my post, the 7s55 is nothing more than a 7s35 with a decorated oscillating weight. It’s not even close to the 4R35 in terms of power reserve, features (hackable and hand-windable) and accuracy, let alone the 6R35.

Sorry to break out the not-so-inspiring news, but that’s the way it is.

Quartzimodo Admin.

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