After reviewing calibers 6R15, 7S26, 8L35 and 4R35, we have decided to have a deeper look at 4R35’s close cousin - 4R36 movement. In 2019, Seiko launched new Seiko 5 Sports line with 4R36 in all 27 watches in the collection, so let’s see what makes it tick.
Seiko caliber 4R36 is another automatic caliber used by Seiko Watch Corp. for their in-house watches. As its predecessor, caliber 4R35, it is a 2011 upgrade of a popular 7S36 movement as it offers the hacking and hand-winding functionality, with addition of day/date display, which is its only difference from 4R35. The caliber 4R36 has a day/date calendar upgrade displayed at 3:00, while caliber 4R35 only displays the date. Everything else is the same, including dimensions, jewels, accuracy, etc.
|Caliber Number||7S36, 7S36C|
|Vibrations Per Hour||21,600 bph|
|Shock System||Seiko Diashock|
|Power Reserve||41+ hours|
|Magnetic Resistance||4,800 A/m (60 gauss)|
|Winding Direction||Not hand-windable|
|Diameter||12”’ / 27mm|
|Functions||Hours, minutes, central seconds, day/date calendar|
|Country of Manufacture||Japan/Malaysia|
|Known Brands||Seiko 5 Sport SNZG15J1 (add more in the comments below)|
|Original information from calibercorner.com|
Now let’s get down to the specifics.
Caliber 4R36 is an automatic movement with 24 jewels and beats at 21,600 beats per hour (6 times per second) which ensures over 40 hours of power reserve. It has a clockwise winding direction and includes Seiko Diashock anti-shock system and an ETACHRON regulator.
The caliber 4R36 is basically a Seiko-only version of the caliber NH36. Seiko Instruments (aka SII) sells the NH36 to other watch manufacturers (so called micro-brand watches).
As its predecessor 4R35, 4R36 comes in two variants: A and B. The A version indicates the first generation so 4R36 and 4R36A are basically the same thing. Caliber 4R36B is expected second generation, yet to be released.
The expected fallout of caliber 4R36 is between +45 / -35 seconds per day. This estimate is based on normal daily wear of the fully wound watch in temperatures from 5 ºC to 35 ºC.
Seiko New Turtle Prospex Special Edition PADI SRPA21 on curved lug Endmill Bracelet
Which watches are run by 4R36?
Caliber 4R36 is mostly found in lower and middle priced Seiko pieces, as well as Seiko Prospex timepieces.
When it comes to Prospex New Turtle series, there are wonderful pieces such as :
As you can see, there are many limited edition pieces with this 4R36 caliber inside.
Regarding Baby Tuna series :
Also have a 4R36 heart.
Seiko Recraft SRPC13K1 Blue Cushion Case 4R36-06G0 on Solid End Massy Mesh Band
Three watches from Recraft line fit into this group:
Seiko SRPC15K1 Black Cushion Case, SRPC16K1 Gold Cushion Case and SRPC13K1 Blue Cushion Case.
Two watches from Monster series also have this caliber in their cases:
Seiko Blue Monster SRP455 Limited Edition 500 pcs and Seiko Prospex Monster SRPD27 Black Dial Dive Watch.
Seiko Stargate II SRP510 on full IP Gold Tone Endmill Bracelet
As far as we know, only one Stargate watch is run by 4R36:
Seiko Superior Limited Edition Stargate II SRP510 Gold Tone Diver.
2019 Seiko 5 Sports - 5 "S"
When it comes to new Seiko 5 Sports collection, all 27 watches (19 different models) are run by caliber 4R36.
Seiko 5 Sports SRPD69K1 Red Suits Style on Endmill Bracelet
Historical overview of Seiko movement releases
Just for a reference, below is a brief timeline of Seiko caliber releases, just so you can see how 4R36 fits the story.
Mid 1996 saw the introduction of caliber 7S26. It was not until late 2005 that the introduction of caliber 6R15A happened. It was based on the 7S but included ETACHRON regulator and Spron 510. In late 2006, caliber 7S26B was released, as a version with ETACHRON regulator. The same year, 6R15B was released and included new parts (barrel and train wheel bridge, centre wheel and pinion, movement barrel, ratchet wheel and its screw and oscillating weight). Around the middle of the year 2008, calibers 4R15 and 4R16 are introduced. They were based on caliber 6R15 but without manual winding and hacking options. The caliber in question today, 4R36A was introduced in mid 2011, along with other 4R3x variants (35, 36, 37, 38, 39), which included upgrades in winding and hacking terms. The end of the same year saw another two releases. The first was that of 6R15C, with addition of one jewel (upgrade from 23 to 24), new barrel, modified ratchet sliding spring and date indicator maintenance plate and new balance wheel. The second was the release of 7S26C that included changes to date mechanism and pinion heights for better hand clearances, plates and balance cock. Early 2019 was marked with the introduction of caliber 6R35.
The 4R caliber family
As far as 4R series is concerned, including now relatively common caliber 4R36, all calibers in it beat at 21,600bph. Below is the overview of their main characteristics. All calibers in 4R3x series are using traditional mainspring, instead Spron 510 found in more expensive pieces.
Caliber 4R36 is relatively new caliber that is a ticking heart of quite a few nice watches on the lower and middle end of the price range. But the real point here is that it has everything one needs from a watch movement. In the end, it’s Seiko’s caliber, so it’s surely well made.
Written by M.H. , Photo by Toni
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