Seiko SII Caliber NH35

Seiko (SII) Caliber NH36

Seiko SII Caliber NH35

Manufacturer Seiko
Caliber Number NH36A (aka NH36)
Movement Type Automatic
27.40mm (outside) / 29.36mm (casing)
Jewels 24
Vibrations Per Hour
21,600 bph
Lift Angle 53 degrees
Shock System Diashock
Power Reserve
41 hours
Rotor Direction
Bi-directional winding (Magic Lever)
Hacking? Yes
Hand-Windable? Yes
Manual Winding
Clockwise direction
Hand Sizes
1.5mm / 1.0mm / .21mm
351-200 / 351200 (tap 10)
Functions Hours, minutes, central seconds, date calendar
Country of Manufacture Japan or Malaysia (see below)
Known Brands
Seiko, Invicta, Vostok, Lum-Tec, Spinnaker, Minus-8 Layer, Advisor AstroHelm, Advisor Ascent (Add your watch in the comments below…)

The Seiko Instruments (SII) caliber NH36 (NH36A) is a hand-windable, hacking upgrade from the Seiko caliber NH26A (read: NH25A vs NH35A). Seiko Instruments labels the NH calibers as part of the “Basic” Mechanical Series.

NH36A VS 4R36A:

It’s also important to note that the Seiko NH36A movement is basically an unbranded version of the Seiko caliber 4R36 found in the Next Generation Orange Monster. In other words, the 4R36 is used in Seiko branded watches, the NH36 is sold to other brands for use in non-Seiko watches.


One of the most popular watch movements available right now is the Seiko Instruments caliber NH35A. The NH35A and NH36A are very similar and both are based on the same Seiko NH family of movements. The main difference is that the NH36A has a complication to display the day of the week and the date, whereas the NH35A only has a date.


In the technical documentation, Time Module claims that the NH36A accuracy range is within -20~+40 seconds per day under normal conditions.

These accuracy measurements were recorded without the date complication being active. This shouldn’t have any noticeable bearing on the accuracy, but it’s interesting.

Note: When you attempt to get a measurement of your watch’s accuracy, it’s important to make sure your watch is fully wound or the lack of power reserve may skew the test results. TMI states that measurements should be done within 10-60 minutes after the movement is fully wound up.

Winding the Mainspring:

The NH36A should be fully wound after about 55 manual turns of the crown. This movement is also equipped with the Seiko Magic Lever, so shaking the watch side to side should get it going almost immediately. You cannot overwind it.

Crown Position Functions:

  • 0 (against the case): Clockwise = Manual Winding / Counterclockwise = Nothing
  • 1 (pulled out one click): Clockwise = Day setting / Counterclockwise = Date setting
  • 2 (pulled out two clicks): Time setting clockwise and counterclockwise

When in position 2, with the crown pulled out two clicks, the seconds hand should stop. This is what is called hacking.

Rotor Variations:

While many watch brands that use the NH36A will opt for a custom rotor (oscillating weight), as of the official tech sheets from March 2017, two stock rotors are available depending on the country of origin: Japan or Malaysia.

Replacement Price:

At the time of this post, replacement prices for the caliber NH36A were found online for around $38.27 USD. Buy it here

Additional Resources:

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2 years ago

Ratio watches use this movement in their freediver range. 1000m water resistance with helium safe crown, altogether with the seiko movement and the 316 case, sapphire glass – Unbeatable rock solid reliable dive watch.

7 months ago
Reply to  Ricado

I have one of the Ratio 1000m meter watches with the sapphire glass and helium release valve. (beautiful lume too) and have adjusted it so the beat error is very low and the watch is accurate to within a few seconds a day. Fantastic value and very reliable.
I also have a Tandorio with this movement in it. It also has sapphire glass and looks very similar to my Seiko SKX007. I have also adjusted this and it has a very low beat error and accurate to about 2-3seconds a day.

11 Лучших Механических Часов для Дайвинга (2022) — Wrist Watch Everywhere
2 years ago

[…] В качестве часового механизма был использован автоматический японский Seiko NH36A. Внутри механизма находятся 24 искусственных камня, частота колебаний баланса 21600 в час, а запас хода 41 час. Механизм обладает двунаправленным подзаводом (источник). […]

1 year ago

Islander Watches use the NH36 and NH35 movements in many of their watches too.

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