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Seiko caliber 8L35 - made to stand the tests of time

July 17, 2019 4 min read 6 Comments


Today we’re going to analyze 8L35 high-end automatic movement from Seiko, for those less familiar with it. Seiko 8L35 is an automatic movement and a close cousin of 9S55 caliber (more about it later) found in some famous Grand Seiko pieces. It is often considered as one of the best Seiko movements out there and compared to RX’s 3135 movement, which is, you must admit, a nice compliment. Seiko 8L35 caliber is one of the first movements assembled in Morioka Seiko’s Instruments Inc. workshop nested in Shizukuishi, under the Mount Iwate mountain and established in 1970. Caliber 8L35 was specially designed for diver’s use.


Disassembled Seiko Marinemaster with 8L35 movement. Original pictures by Adriano @watchprosite.com

What makes it so prized today?

To find out more about Seiko 8L35 Movements Performance, let’s take a look inside Seiko’s caliber 8L35. It operates at 28,800 vph and has 26 jewels. Simply said, that means it holds over 50 hours of power reserves. Its accuracy is high standard and includes hacking and hand-winding options, as it often exceeds the levels of certified chronometers. That brings us to the next point.

Seiko 8L35 accuracy

Just for a reference, some average accuracy of a chronometer is within +/- 6 seconds per day, while Seiko 8L35 accuracy messes no more than -10/+15 seconds per day in normal temperature conditions (5-35 °C). In translation, you won’t even notice it.

Seiko 8L35 vs. 9S55


Grand Seiko 9S55 movement. Original picture from @pen-online.jp

Seiko’s 9S series is considered as one of the finest calibers when it comes to precision. 9S55 is introduced in 1998 as a first Grand Seiko mechanical movement after a 20-year break. Basically, 8L35 is "undecorated and unadjusted" version, or simply said - a base of 9S55. Some even call it a down-market version, as the watches incorporating 8L35 are slightly less priced than those with 9S55 caliber. But it all comes down to refinements and 8L35 is still considered no less worthy than 9S55.

Seiko 8L35 vs. 8L55


Disassembled Seiko 8L55 movement. Original picture from @seikowatches.com


Seiko Watch Prospex SLA025J1 - SBEX007 Hi-beat is powered by the 8L55 caliber with 36,000 vph

8L55 is a year 2009 variation of Grand Seiko 9S85 movement with a bit different finishing. Seiko 8L55 movement is basically a cousin of 8L35, therefore it has some improvements. For example, 8L55 operates at 36,000 vph (8L35 operates at 28,800) and has 37 jewels (11 more than 8L35). Naturally, its power reserves are a bit higher as it can hold around 55 hours. Its higher frequency also makes it theoretically more precise, but these differences are so small that they present no reason to choose one over another, as both of these are high-quality calibers.

Watches with caliber 8L35 & their prices

Many watches that once incorporated 8L35 have the same re-issues, but with same caliber in them, which speaks a lot about this old fella. We can roughly divide them into three model categories.


Seiko Emperor Tuna SBDX016 on Italian alligator watch strap 22B18PBU63A1D26

First of them are Seiko Tuna series, including Seiko Emperor Tuna, modern versions of Seiko’s 6159-7010 Grandfather Tuna. Let’s first mention Seiko 50th Anniversary Diver Prospex Marine Master Automatic SBDX016 (with caliber version 8L35-00J0) introduced in 2000. It is priced around JP432,000 (~$4,000) today.


Seiko celebrates ‘Mobile Suit Gundam’ 40th Years Of Success with 3 Limited Edition Watches!  Read more

When it comes to Emperor Tuna, we must mention two Seiko Gundam, the largest “Emperor Tuna”. Seiko celebrates ‘Mobile Suit Gundam’ (Japan’s most popular anime series) 40th years of success with 3 limited edition watches; two of them are Emperor Tuna. Seiko Prospex SBDX029 (SLA031) Marinemaster 1000M Char’s Zaku II Limited 1,000 and Seiko Gundam Prospex SBDX027 (SLA029) Marinemaster 1000M Zaku II Limited 1,000, introduced in 2019 is on the higher end with price over $4000.


2015 Seiko Emperor Tuna SBDX013 on Zulu

Plus, there are two models from 2015, labeled as models SBDX013 priced around $2,600 and SBDX014 can be found around $3000.


Seiko Marine Master SLA019J, Two fitted watch bands, Left : on  Super Engineer II Bracelet  , right : on Hexad Bracelet

Another series is Seiko Marinemaster 300m, simply marked as MM300, newer versions of the legendary model SBDX001, nowaday this dis-continued model is hard to find one in new, that's why the price is up for around $4,000. Some other modern MM300 watches housing 8L35 are Seiko 1968 Divers 50th Anniversary Deep Forest Green Marine Master SLA019J (marked 8L35-00S0) priced around $3,600 and Seiko Prospex Marinemaster MM300 Diver Automatic SBDX017 (with mark 8L35-00K0), which price can also be found below $3,000 , pricing is more less the same as model SLA021J1.


Seiko Prospex Diver SLA017 on 19mm Super-O Boyer Bracelet, View ALL 19mm stainless steel watch bands

The third Seiko model category with 8L35 inside is the re-issue of 62MAS, Seiko Prospex Diver SLA017 (with mark 8L35-00N0) with its limited edition going up to over $6,000 and re-issue of vintage Seiko 6105 dive watch, Prospex 1970 Diver’s Re-Creation Limited Edition SLA033 priced around $4,500.

When it comes to prices, on the lower end, the starting price would be around $2,600 for some SBDX013 pieces. Other than that, all models of watches having 8L35 inside are over that price.

Is Seiko 8L35 movement worth the money?

When you take into account that this caliber is proudly standing through all tests of time, then the price of watches completely justifies all of its flaws, even compared to some newer movements. In the end, these flaws, or better said differences, cannot really be taken into the account as you probably won't even notice them. In the end, we speak about high-end calibers here. In conclusion, not only that any watch with caliber 8L35 won't be a wrong choice, but rather, by wearing one of this watches, in Seiko's words: you’ll be honoring the origins while embracing the future. And honestly, is there a better way to describe this magnificent caliber?

We don't think so.


Shop  Seiko Stainless Steel Replacement Watch Bands for MM300

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:

6 Responses

Harvey Ito
Harvey Ito

March 20, 2023

I’m so tired of Seiko being opaque about accuracy? I’ve tweeted hundreds of tweets on (I can say this…) being inscrutable, perpetuating an old stereotype… be brave, bold, honest, sincere! They have a solid movement, just that they’ve devoted a minimal production line at the Shizukuishi watch studio ( manually “adjusted” not regulated like a proper Swiss Company… certified chronometers need (5 days, 6 positions, etc..) is Prospex going to commit people to do this? I purchased the new SLA 069 with the 8L35 movement. My next purchase, I’m considering a Longines Majetek Pilot Watch (COSC) or a Chronomaster (High-beat COSC).

Reggie VanNess
Reggie VanNess

September 15, 2022

I have two Seiko Samurais divers watch 4r35 movement one of those is running just a bit slow within a 14to20 day Cycle my plan is to have it served just for a little improvement i really don’t mind if I’m running a bit fast! My future plans are to go with a Is Marine Master i love Seiko Divers watches and I’m hungry for Knowledge !

James Blamire
James Blamire

June 09, 2022

I agree that Seiko overstate their accuracy range on many of their models, I have had a couple of 6R35 movements that were well within COSC range on the wrist straight out of the box. Ask anyone with a SARB033.

Shaun Kamark
Shaun Kamark

March 27, 2020

my SBDX017 has and is always on my wrist and hasn’t loss any seconds for few months at a time! Maybe every 3 half months I lose almost a minute that’s it!! Incredible watch and movement!


March 19, 2020

SEIKO always overstate tolerance ranges. Their movements tend to perform much better than stated. The -10/15 in reality is much more narrow (perhaps —8/8 or COSC). I have seen a MM300 do +1 second a day.

Carl Berenson
Carl Berenson

January 08, 2020

The Seiko 8L35 is accurate to within 10-15 seconds a month not per day!!!

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