Seiko Caliber NHxx Variation Differences Watch Movement

Since it was introduced, Seiko’s NH family of movements has boosted the affordable watch market, and has arguably provided a stable platform for many microbrand watches to exist. The NH series is a solid workhorse movement with functionality that is desired in modern watches. In this article, Caliber Corner is going to discuss the differences between all of the NH variants.

Some of the topics covered in this caliber listing:

• What is the difference between Seiko/TMI/SII “NH” calibers?
• Main Differences
• Specs Comparison
• Year Introduced
• Accuracy
• Difference Between Crown Functions
• Which NH caliber movement does my watch have?
• Which one is better?
• Ladies and midsize NH calibers
• NH VS NE

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.

• NH34 (Seiko 4R34)
• NH35 (Seiko 4R35)
• NH36 (Seiko 4R36)
• NH37 (Seiko 4R37)
• NH38 (Seiko 4R38)
• NH39 (Seiko 4R39)
• NH70 (Seiko 4R71)
• NH71

There are some differences between these overall similar movements but they are all based off of the NH35 caliber which is based off of the original 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:

NH34A	NH35A	NH36A	NH37A	NH38A	NH39A	NH70A
3 Hands	No	Yes	Yes	Yes	Yes	Yes	Yes
Date	Yes	Yes	Yes	Yes	No	No	No
Day	No	No	Yes	No	No	No	No
24 Hr Dial	No	No	No	Yes	No	Yes	No
Skeleton	No	No	No	No	No	No	Yes
GMT Hand	Yes	No	No	No	No	No	No

Specs Comparison:

NH34A	NH35A	NH36A	NH37A	NH38A	NH39A	NH70A
Origin	Japan/Malaysia*
Diameter	12”’ (27.40mm)
Casing Diameter	29.36mm						27mm**
Height	5.32mm
Jewels	24
Power Reserve	> 41 Hours
Beat Rate	21,600 vph (6 vibrations per second)
Lift Angle	53 degrees
Accuracy	-20~+40 seconds/day***
Hacking?	Yes
Hand-Windable?	Yes
Winding Direction?	Bi-directional
Shock-Absorber	Seiko Diashock
COSC?	No

*Country of origin with these movements is debatable and unconfirmed. Yourself or parts sellers and YouTubers may choose to be firm in a certain belief of where they are manufactured, but that doesn’t change the fact that most of these movements are not actually stamped with a country of origin. What we do know for sure is that only the “Japan” marked movements were actually made in Japan, and apparently they stopped making them there a long time ago.

**The diameter of the movements is basically the same, but the reason the NH70 has a smaller casing diameter is because the other calibers have a plastic “dial holding spacer” surrounding the movement. This is the piece that the dial feet go into. Since the NH70 is a skeleton dial, it is not designed to be used with a dial, therefore no dial holding spacer, resulting a smaller casing diameter.

***This is factory spec, but these movements can be regulated to perform better.

Year Introduced:

NH34A	NH35A	NH36A	NH37A	NH38A	NH39A	NH70A
Year Introduced	2022	2011?	Unknown	Unknown	Unknown	Unknown	2017

Accuracy:

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	NH34A	NH35A	NH36A	NH37A	NH38A	NH39A	NH70A
0	Clockwise: Manual Winding Counterclockwise: Free (does nothing)
1	Clockwise: Sets the GMT hand Counterclockwise: Sets the date (quick set)	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
2	Time Setting				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 is 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

NH VS NE:

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