Seiko (SII) Caliber NH35A

The Seiko/TMI/SII caliber NH35 (NH35A) is a hand-windable, hacking upgrade from the Seiko caliber NH25A (read: NH25A vs NH35A). The earliest documentation on this movement that we were able to find was issued on 2/14/2011, this also corresponds with the 2011-2012 time frame that the first NH35A powered watches started hitting the market.

The NH35A is currently one of the world’s most popular automatic movements and is widely available in many affordable/microbrand watches.

Time Module aka Seiko Instruments labels the NH calibers as part of the “Basic Mechanical Movement” Series. They also have NE calibers that are labeled as “Premium” Mechanical Series.

NH35A Also Known As…

It’s also important to note that the Seiko NH35A movement is basically an unbranded version of the Seiko caliber 4R35. for example, the NH36 is an unbranded version of the 4R36 (day + date) found in the Next Generation Orange Monster. Read: NHXX caliber differences.

Accuracy:

In the technical documentation, Time Module claims that the NH35A accuracy range is within -20~+40 seconds per day under normal conditions. They recorded these accuracy measurements without the date complication being active. This shouldn’t have any noticeable bearing on the accuracy, but it’s interesting nonetheless.

Note: When you attempt to get a measurement of your watch’s accuracy, it’s important to make sure your watch is fully wound or the lack of power reserve may skew the test results. TMI states that measurements should be done within 10-60 minutes after the movement is fully wound up.

Winding the Mainspring:

So what does fully wound up mean? The NH35A should be fully wound after about 55 manual turns of the crown.

This movement is also equipped with the Seiko Magic Lever, so shaking the watch side to side should get it going almost immediately.

Crown Position Functions:

0 (against the case): Clockwise = Manual Winding / Counterclockwise = Nothing
1 (pulled out one click): Clockwise = nothing / Counterclockwise = Date setting
2 (pulled out two clicks): Time setting clockwise and counterclockwise

Reference Variations:

The NH35A has several variations depending on a few variables. While all are considered to be “NH35A”, there can be different reference numbers based on each combination of variable options. This information is mostly useful for watch manufacturers, but can also be useful if you intend on swapping your movement for any reason. The variations include the location where the movement was produced, date position, calendar color, and hand fitting type.

Date Position

From the factory, the NH35A has the date at 3:00 or 6:00. The 3:00 date version is the most common.

To determine which date position your raw movement has, point the crown to the right and look for the number that reads from left to right – is it at 3:00 or 6:00? The location will determine the way the dates are printed on the datewheel. If your watch has a date in a different location, say a tilted date at 4:00, then it means the watch manufacturer used an NH35A with a 3:00 date position and cutout the date window at the 4:00 position.

Also keep in mind that although unlikely, it is possible the watch manufacturer printed a custom datewheel – again, possible but unlikely.

Date Disc Color

The NH35A datewheel (aka date disc) is available from the factory in two versions: white background with black text, or black background with white text. The white datewheels with black text are the most common. Some watch brands choose to customize their datewheels to have different colors or font types.

Country Code

Part of the reference number also determines the origin of production (see the rotor section below). J is for Japan, M is for Malaysia. The majority of NHXX movements are made in Malaysia now.

Hand Fitting Type

NH35A movements can be made for Hand Type M or L. Type L is like a high hand version. This affects the overall height of the movement from the bottom to the top of second hand pinion. The thickness of the NH35A is 5.32mm, but the overall height including the hands can be about 7.6mm (M) or 8mm (L).

When designing a watch from scratch, this is useful for determining the thickness of your case, dial, space between dial and crystal, etc. When modding your current watch or swapping movements, be sure that you order the correct Hand Fitting Type or you may end up with hands sticking up too far away from the dial.

Rotor Variations:

While many watch brands that use the NH35A will opt for a custom rotor (oscillating weight), as of the official tech sheets from March 2017, two stock rotors are available depending on the country of origin: Japan or Malaysia.

Update: Many rotors are now without a country of origin stamp (keep reading…)

TMI Rotors:

There are also rotors that are stamped with TMI (Time Module Inc) instead of SII (Seiko Instruments). If you see this, it doesn’t mean your movement is fake, it just means the movement was produced on the TMI side of things.

Update: It is now more common to find TMI rotors than SII. It is becoming nearly impossible to find SII unless it is new old stock.

New Country of Origin Mystery:

What is really the big mystery lately is that many NHXX movements are showing up without the country of origin stamped on the rotor (or anywhere else for that matter). These non-country of origin movement appear to be coming from Chinese suppliers. Does this mean that SII is having the movements made in China but not willing do disclose that fact? Or are Chinese factories (that may or may not have contracts to manufacture movements for Seiko) running off their own batches of NH movements? With the supply of NH movements supposedly running low and prices going up, more and more of these unmarked movements are popping up. If Seiko is having them made in China, they should just disclose that transparently on the rotor, as they do with NH calibers made in Japan and Malaysia. Especially since watches sold in the United States are required to have a country of origin on the movement.

We have reached out to our contact at Seiko with the following email and will update this post if a response is given:

Are there fake NH35 movements?

There was a time when the answer to this was why would anyone bother to fake a $30-50 movement? Times have changed. With the inflated price surge caused by the rapid growth of microbrands and the China produced homage watch market, supply and demand is tainting the waters around the NHXX line. While you may not see blatant fakes of the NH35A, there are clones popping up at half the price, with no text engraved on the rotors (aka sterile). Update: Scratch the last line. Now there are blatant fake NH35A movements out there, be careful!

Yes, there are fake NH35 movements (will try to do a side-by-side comparison eventually).

Is this a result of Seiko using factories in China and then those factories doing what they are well-known for: stealing the design and instead of shutting down the production when the purchase order quantity is fulfilled, just continue production on the same equipment but with subtle changes like not stamping the brand name into the rotor.

Is it a result of the Ali-sellers moving so many watches over the past couple of years that they finally just started to explore sourcing their own copycat movements from within China? The cheap-from-China watch crowd continues to fuel the Ali-Machine and support counterfeiters rather than real microbrands and fellow watch enthusiasts.

Either way, clones and fakes are showing up and they even steal pictures from Caliber Corner to sell their movements. That means you could be buying a fake movement from a seller who is showing you a real movement based on a stolen image from this site. If you see sellers using images from this site (they even remove the watermarks), please report the seller to the platform they are using.

Replacement Price:

At the time of this post, replacement prices for the caliber NH35A were found online for around $38.27-$59.99 USD. Buy it here

Update 10/2021: The cost of replacing an NH35A (and any of the NH series movements) has recently increased to about $60.00 – 80.00 USD in the name of supply/demand and the current “world situation”. Even suppliers with existing stock suddenly increased their prices without warning after seeing other sellers doing it. It’s a dramatic increase in price, and yet to be known if it is justified or worth it. This may also lead to microbrands using more Miyota 8 series movements instead of the NH35. This will inevitably result in an increase in retail prices for watches with this movement, even for watches that are already on the shelf containing movements that were bought at the old prices – such is how pricing works in the watch industry.

Examples of NH35 Powered Watches:

Seiko NH35 movement in a Minus-8 Layer watch

NH35A in a Vostok Jurgis Kairys – notice that this one doesn’t say Japan or Malaysia on the top.

NH35A in a BOLDR Odyssey bronze meteorite dial diver found here.

NH35 Custom Rotor:

Sometimes you can find NH35A watches with a custom rotor. Typically, this is just a sticker placed on the stock rotor. The custom sticker rotor example below was found in this Spinnaker Dumas diver. Notice how it says Japan on it? Based on the country of origin information above, it would be interesting to peel back the sticker to see if it is in fact a Japan stamped rotor.

Another Spinnaker with a similar custom rotor sticker. This time in a Fleuss diver model.

Invicta is also known for using yellow stickers on some of their NH35A powered watches. Below is a bronze Pro Diver. Notice how they didn’t put a country of origin, but they did print U.S.A. Product design on the rotor. A quick glance by an unsuspecting consumer who knows little about watches and calibers, might cause them to think the movement is made in America.

Video Action:

Here is a quick film of an NH35A movement found in a BOLDR Odyssey bronze microbrand dive watch.

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Additional Resources:

• For complete specs and drawings, see this pdf
• Official parts list for caliber NH35A
• Official instruction manual (pdf)
• Also see this thread: NH25A Vs. NH35A Comparison/Differences
• Also read: Seiko NH Caliber Comparison/Differences
• More watches with the caliber NH35 here
• Difference between SII and TMI