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On the trail of great Seiko watch movements... 4R35

March 27, 2019 7 min read 4 Comments

On the trail of great Seiko watch movements... 4R35

The watch movement saga continues with another productive member of 7S family of watch movements made by Seiko. As you know, 7S family was introduced in the 90s of the past century. It is referred to as a “mainstream automatic watch movement”, which followed the famous 7002 line from 1988. The design of the watches in the lineage hasn’t changed much with years, but new movements were introduced, to go along with demands on the market.

Regarding the history timeline of 7S family, which started in 1996, the next famous follow-ons were 6R15 (with Spron* 510), introduced in 2006 and 4R15 from 2008. Calibers 4R15/4R16 were based on 6R15 containing Spron 510, but lacked hand winding and hacking options, like their ancestor 7S26. Still, they were made to reduce the cost from 6R15 movement.

strapcode-watch-bands-Spron-alloys-grand-seiko-comimage from grand-seiko.com

For those who don’t know, Spron is short for Spring Micron, a special alloy of mainly Cobalt and Nickel, developed by Seiko for use in mechanical watches. Spron 510 refers to alloy of Cobalt, Nickel, Chromium, Molybdenum and some other metals. It is magnet resistant, has superb elasticity, high durability and great heat resistance. An advanced alloy of Spron alloy (Spron 610) is used in Grand Seiko Mechanical (introduced in 2006) and Seiko’s Spring Drive (introduced in 2005) movements, with over 72 hours/3 days of power reserve.

Back to the history class, as 4R15/4R16 movements needed improvements in terms on manual hacking and winding options, 2010 brought the next successor: 4R35, along with other closely related members of this family of movements in 2011: 4R36, 4R37, 4R38 and 4R39. And if all this sounds confusing and too much, let’s just say that the journey from the start of 7S series to the 4R36 was quite long.


But enough with the history, let’s talk specification.

Seiko caliber 4R35 comes in 2 variants: with 23 (4R35A) and 24 jewels (4R35B). Today we’ll explore the B variant, as the A version was revised shortly after its introduction, so the B version took the lead. Seiko 4R35 operates on 21,600 vibrations per hour, meaning it beats 6 times in a second – same as his grand-grandfather, 7S26. It also holds the same power reserve of roughly 41 hours. What is different, though, are hand winding and hacking options. Regarding its durability, it is made to last and withstand a lot, as well as all the calibers in lineage before it, so that isn’t in question at all here. But let’s see how watches with 4R35 behave to find out more.

Seiko’s 4R35 is featured in 2 lines of watches. The first one is popularly called Samurai and the other is so called Mini Turtle or even Baby Turtle both from the Prospex family.


The Seiko Samurai Prospex Automatic Diver

When it comes to Samurai line of Seiko watches, let us first mention Seiko Samurai Prospex Automatic Dive Watch SRPB51 (case mark: 4R35-01X0), shortly marked as Seiko-Samurai-SRPB51. The whole Prospex series is greatly appreciated among diving watches but SRPB51 may be the finest representative of the Samurai line. It keeps somewhat classic line of design common to all Seiko divers in this lineage, but the famous LumiBrite works wonders on its rocket hands in dark environments, whether it is the depth of the ocean, since it is water resistant up to 200 m, or dark night in the woods or a dancing club. We’d say a fella that looks fabulous on any strap and also does the works. Today, you can grab one online for the price of $300 and up at Amazon.


Rubber Watch Bands from Crafter Blue

Seiko Samurai Prospex Automatic Dive Watch Special PADI Edition SRPB99K1(case mark: 4R35-01X0, meaning its face looks pretty much as the previously mentioned), often referred to as Seiko-Samurai-PADI-SRPB99 is another Prospex watch worth mentioning here. The special PADI diver's watches with the PADI logo on the dial and with the red and blue PADI colors on the bezel. It is a pretty good catch for those who would like some contrast. It does capture attention at the first sight when compare with SRPB51. The prices you can find at Amazon today is from $314 up and the functional features are the same as in SRPB51. As a cross-over version, we’d say it is a great value for the money.


With Seiko Watch Prospex Save the Ocean Special Edition Samurai SRPC93K1 (case mark: 4R35-01X0, as two previous models), it can also be found from $300 and up. Another blue Samurai is Seiko Prospex Samurai SRPB09 Blue Lagoon, back with a new blue configuration, called "Blue Lagoon" and indeed they bear striking resemblances to the neon Curacao-laden cocktail of the same name. Offered in a limited edition of 6,000 pieces worldwide and official price is under $600 each, however, nowadays is hard to find one. “Save the Ocean” edition actually contains three watches, this one for Samurai series and SRPC91K1 for Turtle and SSC675 for Solar. While "Blue Lagoon" edition actually contains two watches, one for Samurai series and SRPB11 for Turtle. What make this fella special, besides its color, are his robust lugs, which makes it look quite powerful.


NATO strap - Glow in the Dark

In the same price range is also Seiko Samurai Prospex Automatic Dive Watch SRPB55K1 PVD Black (4R35-01V0), also called Seiko-Samurai-SRPB55. It’s actually a re-edition of the SBDA033 from 2004, also falling in Samurai line. LumiBrite on its rocket hands has the same effect as on SRPB51, but our guy here is maybe a bit more classy or rather elegant, at least when it comes to looks. It is also a watch that falls into the view quite immediately, so if you want to be noticed while wearing a tuxedo, this may be your best bet.


Shop Seiko Replacement Watch Bands for Seiko Samurai


The Seiko Mini-Turtle Prospex Automatic Dive Watches

When it comes to Mini Turtle (Baby Turtle) series, what is worth mentioning? Traditional Black, PADI or Zimbe limited edition from Thailand?


Seiko Mini-Turtle Prospex Automatic Dive Watch SPRC41K1 (PADI Edition) Pepsi Bezel (case mark: 4R35-02K0) -      Seiko-Mini-Turtle-SPRC41 - in short and Seiko Mini-Turtle Prospex Automatic Dive Watch with Black Dial SRPC35K1 (case mark: 4R35-10Y0) or simply Seiko-Mini-Turtle-SRPC35.


Mini Turtle replacement watch bands

Seiko Mini-Turtle Prospex Automatic Dive Watch SPRC41K1 (PADI Edition) Pepsi Bezel is quite a piece of charm. Its round case somehow perfectly fits around its Pepsi bezel. The hands are arrow and sword combination over stylishly designed hour markers. Pack all that on the black dial and you’ll get a nice timepiece, more than worth its price going from $427 and up at Amazon.


2019 Thailand limited edition Seiko Zimbe No.10 Mini Turtles Green Dial SRPD17 and Yellow Dial SRPD19.

Shop Seiko Replacement Watch Bands for Seiko Mini Turtle


Compare the Seiko Calibers

As we already compared 4R35 to its ancestors, let’s see how their timepieces compare.

When it comes to the Samurai line, let’s first compare it with watches run by 7S26 caliber, so SKX watches. The price are somewhat the same, but Samurai is a step up here the same way caliber 4R35 is a step up to caliber 7S26. Hand wining and hacking are probably the only reason for the win of Samurai here.

This gets us to the watches run by caliber 6R15, Sumo, which kind of rules the Prospex line with a few exceptions falling into watches run by 4R35, Samurai. The difference between 6R15 and 4R35 is that 6R15 includes Spron 510 and 4R35 is a traditional movement, so it really comes down to it and whether you prefer former or latter. Statistically speaking, watches in the Prospex line run by 6R15 have more limited editions than watches run by 4R35 movement from Samurai line, so it may be that watch lovers prefer Spron. The price is also slightly higher on 6R15’s end, which runs the part of Prospex called Sumo line. This includes some fine watches such are Seiko Prospex Sumo PADI SBDC049 Diver 200m Limited 1000 Pcs and Seiko Sumo SBDC027 Prospex Diver Automatic 50th Anniversary Limited Edition.

Judging by all the facts, 4R35 is surely a great movement incorporated in some excellent timepieces and yet falling into affordable group. But when compared to all others in its lineage, its ancestors are slightly falling behind, except 6R15 that may be slightly more interesting. That still doesn’t mean anything bad for 4R35, but it’s rather an observation. What we haven’t do here is that we haven’t compared it to its close relative, 4R36, also introduced in 2010, but that movement is still left to be explored in our future posts. That way we’ll have more information on the other contestant so we can draw the clear line. All in all, if you still wonder who the winner here is, ask yourself these two questions:

  • Do you prefer traditional movements over those with Spron?

If the answer is yes, than your winner may be 4R35. If the answer is no, 6R15 may be right for you.

  • Which lines of watches do you like better, Sumo or Samurai?

Sumo will make 4R35 your winner, while Samurai will take the trophy to 6R15.

In our humble opinions, the functional difference between the two is minimal. The second question is far more important. In the end, you’ll be far more happier buying things that you like, than based on minor differences in how their built. Because one thing is sure with Seiko – both movements will work impeccably and you’ll surely have one of the best movements out there, no matter which one you choose. And when you don’t have to compromise on the brains, you also shouldn’t compromise on the look. Or, said in words of American poet Richard Eberhart:

“Style is the perfection of a point of view.”


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:



4 Responses


September 28, 2023

4R35B has 23 Jewels and it comes with the 📅 date which the former 4R35 lacks. Everything else stays unchanged.


June 27, 2023

Love this website! I always wanted to know more about Seiko movements and it’s great to find it all here. Your writing style makes for a good read as well and your passion comes across in the text. Keep it going


April 29, 2022

Seiko prospex samurai, serial number 754687,4r35-01v0, where was it made ? Thank you.


February 17, 2022

Hint, the 23 jewels for the 4r35 family of movements is correct. The 4r36 has the extra jewel for a total of 24 jewels because it has the added complication of a day wheel, which the 4r35 doesn’t have.

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