Seiko (SII) Caliber NH35a Movement

Seiko (SII) NH35/NH35a Movement

The Caliber NH35 (also known as NH35A) is one of the most popular movements on the market that you can buy. The NH35 is essentially a non-branded version of the Seiko Caliber 4R35, but with much more accuracy. It’s a popular choice for modders and hobbyists as an affordable-yet-reliable movement with decent specs.

“NH35” and “NH35a” refer to the same caliber and are used interchangeably.

Caliber NH35a Specs

NH35 movement
NH35 Movement
Outside Diameter27.40 mm
Casing Diameter29.36 mm (with dial holding spacer)
Total Height5.32 mm
Winding MechanismAutomatic, Manual
Jewels24 jewels
Accuracy-20 / +40 seconds per day
Shock ResistanceShock-absorber device
Vibrations (seconds)6
Vibrations (hours)21,600
Power Reserve41+ Hours
Anti-magnetism DC : ≧ 4800 A / m
Lift Angle53 degrees
Hacking / Hand-winding?Y / Y

NH35 Accuracy

Accuracy is a tricky topic because it’s subjective from individual movement to movement. Time Module (TMI), which manufactures the NH35, specifies that the caliber is accurate to

-20 ~ +40 seconds per day (23º± 2ºC)

-TMI Manual

When a manufacturer states the accuracy range of a movement, this typically refers to the rating, but watches are almost always more accurate than that.

Owners of NH35 watches report extreme accuracy in the first day (+1 second) down to -10 seconds towards the end of the initial power reserve. While impressive, extreme accuracy is common in new watches, and you should really measure after a year or more of “breaking in” time. Over the long term, users typically report an accuracy in the range of +/- 20 seconds per day, which is very similar to what users report of the 4R35.

Watches with the Caliber NH35a Movement

Since the Caliber NH35A is so cheap and easily obtainable, many watch brands use it as the main workhorse movement in their lineup. They are primarily used by lower-priced microbrands. More expensive microbrands justify their price by using a Swiss ETA movement.

Here are a few brands known to use the NH35:

  • Seiko
  • Invicta
  • Helm
  • Lum-Tec
  • Unimatic
  • Orion
  • Geckota
  • Benarus
  • Spinnaker
  • AVI-8
  • Orthos
  • MWW
  • Scurfa
  • Air Blue
  • Dan Henry
  • Armida
  • Binger
  • G. Gerlach
  • Burei


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NH35 vs NH36

NH35a vs NH36A comparison
NH35 with date (left) vs NH36 (right) with day and date

The NH35 is identical to the NH36 with one difference: The NH35 has a date complication, the NH36 has a day-date complication. In other words:

NH35 (Date) + Day = NH36

NH35 vs 4R35

Caliber NH35 vs cal 4r35
NH35 vs 4R35

The NH35 is commonly known as the “unbranded 4R35.” The 4R35 is the official Seiko movement, while the NH35 is produced by Seiko Instruments Inc. (SII). The NH35 movements are more commonly available for purchase, and are much more affordable. The main difference is that the NH35 is much cheaper and more accurate than the 4R35, and is therefore a preferable choice, all else considered.

However, when people compare the two, they typically say how much more accurate the NH35 is. This is an unfair comparison because their Seiko 4R35 watches are much older and have had their breaking-in period. Ultimately, the accuracy of the 4R35 is very similar.

Watches that use the 4R36 (date) movement include:

  • Seiko Samurai
  • Seiko Presage Cocktail Time
  • Seiko Mini Turtle

Watches that use the 4R36 (day-date) movement include:

  • Seiko Turtle and King Turtle
  • Seiko Monster (4th Gen)
  • Seiko 5 Sports ‘5KX’
  • Other Seiko SRP models

NH35 vs 4R35 Specs Comparison

Movement TypeAutomaticSame
Outside Diameter27.40 mmSame
Total Height5.32 mm Same
Winding MechanismAutomatic, Manual Same
Jewels24 jewels23 / 24
(Seconds per day)
-20 / +40 +45 / -35
Vibrations (seconds) 6Same
Vibrations (hours)21,600 Same
Power Reserve41+ Hours40+ Hours
Lift Angle53 degreesSame
Hacking / Hand-winding?Y / Y Same

NH35a vs Miyota 9015

Caliber NH35a vs Miyota 9015
Caliber NH35a vs Miyota 9015

The Miyota 9015 is a popular choice for watches due to it’s smaller size, hacking + handwinding capabilities, and having a higher-beat movement (28,800 bph). In addition, it’s much more accurate than the NH35 at -10 / +30 sec/day.

Miyota is made by Citizen Watch, and is their movement house. They supply movements to independent watchmakers, and may be as widely-used as SII’s NH35.

NH35 vs 4R36 Specs Comparison

CaliberNH35Miyota 9015
ManufacturerSeiko (SII)Miyota (Citizen)
Movement TypeAutomaticAutomatic
Diameter27.40 mm26 mm
Total Height5.32 mm3.9 mm
Winding MechanismAutomatic, Manual Automatic, Manual
Jewels24 jewels 24 jewels
(Seconds per Day)
-20 / +40 -10 / +30
Shock ResistanceShock-absorber deviceParashock
Vibrations (seconds)6 8
Vibrations (hours)21,60028,800
Power Reserve41+ Hours42 Hours
Lift Angle53 degrees51 degrees
Hacking / Hand-winding?Y / Y Y / Y

NH35 vs 7S26

caliber nh35 comapred to the caliber 7s26
NH35 vs 7S26

The Seiko caliber 7S26 is one of Seiko’s cheaper movements, and is far outclassed by the NH35. Seiko only uses the 7S26 in their cheapest automatic watches, usually the Seiko 5s.

Notably, the 7S26 has a slightly worse accuracy than the NH35, and also doesn’t have hacking or hand-winding. While it has served as a reliable workhorse movement until recently, it’s now time for Seiko to use a more modern movement, and the NH35 is a good start.

Watches that use the Caliber 7S26 include:

  • Seiko 5 Sports SNK809 series
  • SKX Divers (SKX007, SKX009, etc.)
  • Seiko Recraft
  • Many other Seiko 5s

NH35 vs 7S26 Specs Comparison

ManufacturerSeiko (SII)Seiko
Movement TypeAutomaticAutomatic
Outside Diameter27.40 mm27.40 mm
Casing Diameter29.36 mm (with dial holding spacer)27 mm
Total Height5.32 mm4.8 mm
Winding MechanismAutomatic, ManualAutomatic Only
Jewels24 jewels21 jewels
(seconds per day)
-20 / +40-20 / +49
Shock ResistanceShock-absorber deviceDiashock
Vibrations (seconds)66
Vibrations (hours)21,60021,600
Power Reserve41+ Hours 41+ Hours
Anti-magnetism DC : ≧ 4800 A / m DC : ≧ 4800 A / m
Lift Angle53 degrees 53 degrees
Hacking / Hand-winding?Y / YN / N

NH35 vs 2824-2

caliber nh35 compared to ETA 2824-2
NH35 vs 2824-2

The 2824-2 is one of the most recognizable Swiss movements. It comes in many different grades, and many watch manufacturers will tweak it and call it a proprietary caliber; as such, it is considered a base caliber that is often modified and decorated.

Not only is the 2824-2 more accurate than the NH35, but it’s reliable from the perspective of staying close to its specifications over the long term. As the most common Swiss movements, it is the cheapest to Swiss movement to service.

A standard grade 2824 movement is adjusted in 2 positions, while the NH35 is not adjusted. This makes it less likely to be regulated too accurately.

NH35 vs 2824-2 Specs Comparison

ManufacturerSeiko (Japanese)ETA (Swiss)
Movement TypeAutomaticAutomatic
Outside Diameter27.40 mm25.60 mm
Total Height5.32 mm4.6 mm
Winding MechanismAutomatic, Manual Automatic, Manual
Jewels24 jewels17 / 21 / 25
(seconds per day)
-20 / +40+/- 12 to 30
Vibrations (seconds)68
Vibrations (hours)21,60028,800
Power Reserve41+ Hours 38+ Hours
Anti-magnetism DC : ≧ 4800 A / m DC : ≧ 4800 A / m
Lift Angle53 degrees 53 degrees
Hacking / Hand-winding?Y / YY / Y

The NH35a in the Invicta 8926OB

Th3 NH35A movement in the Invicta Pro Diver 8926 with yellow rotor

The Invicta Pro Diver uses the NH35A movement in it’s automatic model 8926OB. This watch has a clear caseback, and the distinguishing thing about it is the yellow Invicta rotor, which reads:




Invicta Watch Company

Since 1837

A lot of people love to hate Invicta, but sometimes they add nice details even when they didn’t have to. The decorated NH35A movement in yellow is one of those details.

Furthermore, consider that the price of the Invicta 8926OB is just $40 more than the movement itself… and that this includes the movement. If nothing else, that speaks to the good value of the automatic Invicta Pro Diver.

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