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Seiko Tmi Nh Caliber

Seiko Caliber NHxx Variation Differences

Seiko Tmi Nh Caliber

What is the difference between Seiko/TMI/SII “NH” calibers?

As of this post there are 10 calibers in the current line of NH “Basic Mechanical Series” movements. We will focus on the main 6 variations based on the NH35, information about the other four will be at the bottom of the page.

Mens size watches

  • NH35 (Seiko 4R35)
  • NH36 (Seiko 4R36)
  • NH37 (Seiko 4R37)
  • NH38 (Seiko 4R38)
  • NH39 (Seiko 4R39)
  • NH70

There are some differences between these overall similar movements but they are all based off of the original NH35 caliber which is based off of the NH25. The differences are mostly related to day/date/24 hour indicator. Please compare in the chart below. Did we miss anything? Please comment below.

Main Differences:

3 Hands Yes Yes Yes Yes Yes Yes
Date Yes Yes Yes No No No
Day No Yes No No No No
24 Hr Dial No No Yes No Yes No
Skeleton No No No No No Yes

Specs Comparison:

Origin Japan/Malaysia
Year Introduced 2011? Unknown  Unknown Unknown  Unknown  2017
Diameter 12”’ (27.40mm)
Casing Diameter 29.36mm  27mm
Height 5.32mm
Jewels 24
Power Reserve > 41 Hours
Beats Per Hour 21,600 vph (6 vibrations per second)
Lift Angle 53 degrees
Hacking? Yes
Hand-Windable? Yes
Winding Direction? Bi-directional
Seiko Diashock


Time Module claims that the NH calibers are rated for static accuracy of -20 ~ +40 under normal temperature conditions. All measurements are done without the calendar function, as well as within 10-60 minutes while fully wound.

Difference Between Crown Functions

As we see here, the main differences between the two calibers is that the NH35A is hackable and can be hand-wound. That means the crown operates differently:

 Crown Position NH35A NH36A NH37A NH38A NH39A NH70A
  • Clockwise: Manual Winding
  • Counterclockwise: Free (does nothing)
  • Clockwise: Nothing
  • Counterclockwise: Sets the date (quick set)
  • Clockwise: Sets the day
  • Counterclockwise: Sets the date (quick set)
  • Clockwise: Nothing
  • Counterclockwise: Sets the date (quick set)
Time Setting Time Setting Time Setting
Time Setting None None None

Which NH caliber movement does my watch have?

Unless the manufacturer installed a custom rotor, the caliber number should be engraved or stamped there. If it has a closed caseback or custom rotor, you can tell by looking at the complications on the dial. Of course, it’s always possible that the manufacturer made their own modifications or removed some features that didn’t correspond with the watch design (say for example they got a really good deal on 200 NH35A but the watch doesn’t have a date window, they could just use the NH35A without the date).

Which one better?

It really depends on what you need from a watch! If you like simple minimalist 3 hand watches, then the NH38A is for you. If you like have a 24 hour subdial, then go for a watch with the NH37A. Let the community know which caliber you prefer and why in the comments below…

Ladies and midsize NH calibers:

  • NH05
  • NH06
  • NH15
  • NH16


TMI aka Seiko Instruments markets the “NH” calibers as “Basic” Mechanical Series. They also have “NE” calibers that are marketed as “Premium” Mechanical Series.


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Wes Nicholson
Wes Nicholson

HI! I have a modded 7s26. It gains 15mins per day when worn, but maybe 2mins per day when not worn. I want/need a more accurate movement. I don’t have “day”, “date” or “24hr” requirements. Just the 3 hands and accuracy are required. What do you recommend would fit? Will the NH70 fit? Thanks


the NH70 is on point accurate since a week. Now i am looking at my laptops time. its says 10:13 and my NH70A caliber shows me 10:13. Last time i adjusted the time, was when i bought it, 2 weeks ago. So accuracy …nailed it!

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mark wolfson
mark wolfson

My Invite Pro Diver 8926OB has the NH35A just purchased August 2019. However, it functions differently than described above. First, when pulled out to ‘zero,’ it feels free with no feel of any attachment of crown moving the winding p Iart of movement. Am I winding, going clockwise with no feel of friction? Next, the watch does not stop when crown pulled out to 2nd click. So hacking (synchronizing second hand to minutes hand at 12 o’clock position) does not happen this way. However, I can freeze the hands if when setting time, I go very slightly counter-clockwise, then wait… Read more »

Eddie M.
Eddie M.

Maybe you can try posting this on the NH35A thread and see what they say over there. Do a search.

mark wolfson
mark wolfson

Sorry it is an Invicta, not Invite, sorry for auto spell