Seiko SII TMI NH25A vs NH35A Differences Compared

Seiko Caliber NH25A VS. NH35A

Seiko SII TMI NH25A vs NH35A Differences Compared

What is the difference between Seiko caliber NH25 and NH35?

There are some differences between these overall similar movements. The differences are mostly convenience that give value to the collector. Please compare in the chart below. Did we miss anything? Please comment below.

Seiko Caliber NH25A Seiko Caliber NH35A
Seiko Caliber 7S25 4R35
Origin Japan/Malaysia Japan/Malaysia
Year Introduced (Please add to comments below) 2011?
Diameter 12”’ (27.40mm) 12”’ (27.40mm)
Casing Diameter 29.255mm 29.36mm
Height 5.32mm 5.32mm
Jewels 21 24
Power Reserve > 41 Hours > 41 Hours
Beats Per Hour 21,600 vph (6 vibrations per second) 21,600 vph (6 vibrations per second)
Calendar? Yes Yes
Hacking? NO! Yes
Winding Direction? Bi-directional Bi-directional
Hand-Winding? NO! Yes, can also be manual-wind
Crown See chart below See chart below
Shock-Absorber
Yes Yes
Quick Set Date?
Yes Yes
COSC? No No
Models Add yours to the comments below Add yours to the comments below

Accuracy Differences

Time Module claims that the caliber NH25A is rated for a static accuracy of -25 ~ +35 seconds per day. The caliber NH35A clocks in at a static accuracy of -20 ~ +40 seconds per day under normal temperature conditions and without the calendar function. These measurements were taken within 10-60 minutes of being 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:

NH25A NH35A
Crown in position 0 Free (does nothing)
  • Clockwise: Manual Winding
  • Counterclockwise: Free (does nothing)
Crown in position 1
  • Clockwise: Sets the date (quick set)
  • Counterclockwise: Free (does nothing)
  • Clockwise: Free (does nothing)
  • Counterclockwise: Sets the date (quick set)
Crown in position 2 Time setting (second hand keeps going aka “doesn’t hack”) Time setting (second hand stops aka “hacks”)

Does my watch have the NH25A or NH35A movement?

It should say on the rotor. If it has a closed caseback or a custom rotor without any caliber markings, the easiest way to tell is to simply wind the crown (unscrew it first if your watch is a dive watch), is it winding the mechanism? Then it’s an NH35A. Pull the crown out two clicks (to position 2 aka time setting mode), does it stop the second hand? Then it’s the NH35A.

Which one is the better movement?

That is up for debate! We’d love to hear your thoughts in the thread below. Why do you like one over the other? What are the advantages of one over the other?

NH25A VS NH35A Drawings

Seiko SII TMI NH25A vs NH35A Drawings

More information:

Also keep in mind that although the NH25 and NH35 calibers are the most talked about, there is actually a slew of other NH calibers: NH05, NH15, NH06, NH16, NH36, NH37, NH38, NH39, NH70, etc

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Is the Seiko Caliber NH25A VS. NH35A any good? Share your opinions, experiences and watches below... Remember to keep comments respectful and follow our community guidelines.

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Tom
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Tom

Wow, awesome guide! Exactly what I’ve been searching for. You covered everything. A+

Steve
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Steve

I have the NH25A and NH35A. Love them both. Bookmarked the site. Keep up the great work.

Marc
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Marc

another excellent informative post from the editor of the site.

Larry
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Larry

What does the A stand for?

Mark
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Mark

i think it stands for automatic

Myles
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Myles

Hi. “A” is the revision of the calibre.

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[…] Also see this thread: NH25A Vs. NH35A Comparison/Differences […]

IAN
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IAN

You might mention that they both have bidirectional winding

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[…] 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 […]

ID doesn't matter
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ID doesn't matter

Since this is a reference document: 1: This sentence means nothing without a TIME reference: “Time Module claims that both the caliber NH25A and the NH35A are rated for accuracy of -25 ~ +35 under normal temperature conditions”. It’s like saying I’ll see you in 7 or 8, Adios. How about per day, per week per month per year…. NooB’s would appreciate it.
2: Please reference which Seiko branded movements the NH movements mimic, always, i.e. 7S26, 4R35, 6R15 etc. thanks.

Steve
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Steve

Don’t feed the troll.

Gaudin
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Gaudin

Precision + 5 to 0 second per day for NH35A but +or- 7 second during sport daily activity . Not note for temperature.

Syndicated Satellite
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Syndicated Satellite

I noticed a number of watch stores and sellers will wrongfully list their watches as having an NH35A movement, when it really has an NH25A movement.

KeepTheTime.com
Guest

This is true! Not only will some sellers list NH25A as NH35A (because they either don’t know the difference or they simply default to the most popular one), but similarly with the ETA 6497 vs 6498, Miyota 8205 vs 8215, and sometimes even the 7750 vs 7753. We’ve also seen some microbrands incorrectly labeling the movements they use. Interestingly, prior to the so-called ETA crisis that pushed a lot of brands to start manufacturing their own movements or find alternative suppliers, calibers weren’t discussed as much. KeepTheTime is one the few watch shops that has always listed the caliber details… Read more »

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[…] the NH35A is meant to be better. The NH35 has hacking/handwinding where the NH25 does not. SeeSeiko Caliber NH25A VS. NH35A Watch Movement | CaliberCorner.com Reply With […]

Franco
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Franco

Thanks for answering my questions. My new favorite site. Bookmarked! I thought I had a nh35 because that’s what the manufacturer listed it but it’s actually a nh25. Damni

Frank Giann
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Frank Giann

I own over 30 watches with both these movements and they are both great but over the long run the NH25A’s have kept more accurate time. I have this one Invicta F0066 with the NH25 movement. It gains a minute every 60 days. This is absolutely outstanding time keeping and I wear this watch every single day to work.

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