Swiss timepieces were once the king, and the luxury aspiration of every watch connoisseur in the world (at least after the Swiss stopped copying English timepieces) - until the Japanese heavyweight Seiko entered the scene.

After Seiko led the Quartz revolution in the 1970s, the Swiss watch industry cratered and numerous watch companies throughout the world crumbled. 


The epitome of a disruptor. Source: Seiko Watches


Apart from its Quartz product lines, Seiko is also known for their automatic NH calibers, which are the mechanical heart of many timepieces. Seiko 9 series movements are used in exquisite high-end watches, but Seiko also makes popular low-cost automatic movements for many brands large and small.

The Seiko NH calibers, which are based on those in-house movements used in most Seiko Automatic watches and many other well-known brands around the world, are regarded as one of Seiko Japan's key mechanical movements. 


Source: @Humism on Twitter


If you are into Seiko Mod Watches - you already know about the NH35 and NH36 which serve as the workhorse for many a mod. There are some other movements in this family, and they offer unique functions and finishing. 

In this post, we will look at the most significant models in Seiko's NH series, ranging from the classic NH35 to the modern NH71. We think Seiko probably offers the best quality automatic movements for the price on the planet - let us tell you why.


Seiko Instruments Inc. Background

In 1881, Seiko entered the watch industry under relatively modest conditions as just a local watch and jewelry store called "K. Hattori." After a few years, the store's owner, Kintaro Hattori, started manufacturing timepieces under the name Seikosha, which marked the beginning of the Seiko watch brand. 

In Japanese, the brand name for genuine Seiko timepieces is "Seikosha," which means "exactly." Seiko was a part of Japan's late-nineteenth-century watchmaking explosive growth. Kintaro extended his Seikosha enterprise after its success in the 1890s.


The birthplace of many pillars of horology. Source: Strapcode


However, it was not formally recognized until 1937, following the establishment of the company Daini Seikosha Co., Ltd - the forerunner of the current Seiko Instruments Inc. Seiko Instruments is a core company of the Seiko Group. It is also where most watches, including movements, are manufactured nowadays.

The company launched the world's first quartz watch with a CMOS IC in 1970, ushering in a new era for the global watch industry. Daini Seikosha has since expanded into other markets such as North America, Singapore, Germany, and Shanghai.

Seiko watches are manufactured items made up of several components, but the important aspect is that all of those components are manufactured by only two Seiko manufacturers: Seiko Instruments Inc. and Seiko Epson.

Seiko-owned specialized units develop and manufacture everything from hairsprings, chips, hands, and crowns to cases, lenses, and straps. Any movement from Seiko will be good, what matters is how you need it to perform. 


NH35 to NH39 - Similarities and differences

The NH35 (Seiko 4R35), NH36 (Seiko 4R36), NH37 (Seiko 4R37), NH38 (Seiko 4R38), NH39 (Seiko 4R39) are all derived from the 4R3x movement. 

Initially introduced in 2008 by Seiko Instruments Inc., the NH movement line quickly formed a powerful position in the industry due to its long-lasting performance and excellent quality in comparison to other options in the same market segment. 


Pictured, an NH39. Source: All Watch Parts


This prestigious Seiko Caliber is offered in the middle-tier product category, although its use spans a number of price points. 

The Seiko NH family of mechanical movements, in general, operate at a frequency of 21600 bph, which is important for creating the perfect quartet of accuracy, durability, easy maintenance, and energy efficiency. This frequency is shared by the majority of Seiko's other mechanical movements as well. 


Determining the Quality

An ideal automatic watch movement would have manual winding and a hacking second, both of which the five abovementioned Seiko Calibres have. When used on a daily basis, these two features promote its usefulness for anyone who doesn't want to wear a watch all the time. 

The 7S, a legendary workhorse movement, serves as the fundamental building block for the NH movement architecture. This ensures that the NH movements are both durable and effective. 


Source: Seiko Watches


These Seiko movements are the base model for the more advanced Seiko 6R movements, which are built upon the 7S movements. 

Workhorse Movements can be thought of as movements that have a minimalist design with basic features in order to work at full efficiency while still achieving all five of the following criteria: long-term durability, accuracy, reliability, ease of maintenance and repair, and low cost of services.

The Top Choice

The NH35 is probably the best-seller of the bunch. It is a three-hand self-winding movement with date, stop seconds and the possibility of manual winding and has 23 jewels

Economical and complete, the NH35 is even integrated into watches costing less than EUR200. The 4R35 (basically the same as the NH35) movement is used a lot in mid-range models, including the Seiko Cocktail time.

The NH35 is used in both Seiko watches and those sold by third parties. The Seiko model (4R35) uses 24 jewels while the NH35 which is sold to third parties has 23 jewels. The NH35A is an inexpensive alternative to the Swiss 2824-2 and SW200 movements.

The NH36 movement is similar to the NH35 in architecture, including hours, minutes, seconds, date, manual winding, automatic winding, a hacking second, power reserve of roughly 41 hours, and 24 jewels. It adds a day display. 

The Seiko 4R36 movement is found in the majority of Seiko Automatic watches as well as numerous models from other well-known companies around the world. Both the NH35 and NH36 are missing a 24 hour dial.


Lesser Known Movements

The NH37 movement has a similar architecture of the NH36 with an additional 24 hour dial, and excludes the date or day display. The NH38 is the most basic movement, with only three hands and the standard functionality of the 4R3x family. The NH38 is available in watches with basic dials. 


Source: Caliber Corner


The automatic NH39 lacks a date and day display. Machining on the movement's surface gives a three-dimensional appearance that can be used for decorative effect. The movement uses 24 jewels and beats at a frequency of 21,600 beats per hour. The NH39 is often used in open heart watch models. 


NH70 and NH71

The Seiko NH70 and NH71 are latecomers to the NH family. 

The two skeletonized automatic calibers, which are built on the NH3 (NH35A) framework, inherit the characteristic fundamental identifying feature of a 3-hand, 1-calendar, 24-jewel watch with functions including hand-winding, stop-second hand, and automatic winding, with a power reserve of 41 hours. 


The NH71 is best paired with open dials, or at least ones with cutouts. Source: @dlx_customwatch on IG


The NH70 has an accuracy range of - 20 to +40 seconds per day (tested in daily hands-on conditions). Many other documents, on the other hand, claim that the accuracy is in the lower range. This error is likely to be lower when the ambient temperature is stable. 

The NH71 movement has similar architectural and technological characteristics with the NH70 movement. The cosmetic difference between the two Seiko movements is the most significant. The NH70 is coated with nickel while the NH71 has a gold plated finish.


Wrap Up

The Seiko watch company is a force to be reckoned with in the world of watchmaking. 

Here at namokiMODS we offer some of the best Watch mod parts in the market. Our SKX007 parts are built to meet or exceed the quality of Seiko spare parts, and they offer some great style choices too. 

If you are looking for Seiko movements, or other watch spare parts, start with our online catalog. You can’t go wrong with namokiMODS! 

June 22, 2022 — Jeremiah A


Laurent said:

Do you know how much parts there is in a NH35 caliber?

Fernando Rodrigues said:

Os relógios Seiko series NH, têm excelentes movimentos.

Joel Guajardo said:

Very well laid out and explanation of these outstanding Seiko movements and the history behind them.

Thomas Andrew Prince said:

Thank you respectfully for your very informative article!

J.G. said:

“Seikōsha” does not mean “exactly”.

The best translation of 服部精工舎 that I can muster is “Hattori Precision Manufacturing Co.” A certain YouTube channel has been promoting “House of Exquisite Workmanship” as another translation, but I think this is too flowery and reading too much into the individual characters.

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