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Seiko (SII) NH38 Automatic Movement - Open Heart

Genuine SEIKO NH38 Movement with an open-heart display at 9 o'clock crown position. This movement is designed for dials with open-heart window

The TOP choice for movement swap with a direct view of the escapement from the watch face. Appreciating the beauty and intricacy of a mechanical movement.

With two available options:

    Hugely improved on the accuracy! These are regulated by certified watchmakers from 0 to +8 seconds per day.
    Fresh out of the factory defaults without any regulation. Accuracy are in accordance to SEIKO's specification of -20 to +40 seconds per day.
Learn how to upgrade your movement, click here

IMPORTANT: Movement upgrade/swap is ONLY recommended for individuals with the right skillsets and experience. Lucius Atelier is not responsible for any damage to the movement during the fitting process. All movements passed Seiko Instruments Inc. (SII) QC prior to shipping are guaranteed to be a fully functional movement. Given the high degree of DIY nature and Seiko's trade practices, unfortunately, we are unable to accept any returns.

Made by Seiko Instruments Inc. (SII)


    1. Manufacturer Seiko Instruments Inc. (SII)
    2. Caliber NH38A
    3. Movement Type Automatic, Mechanical
    4. Movement Diameter 27.40mm
    5. Casing Diameter 29.36mm (with dial holding spacer)
    6. Movement Height 5.32mm
    7. Jewels 24 jewels
    8. Beats Per Hour 21,600 vph (6 vibrations per second)
    9. Special Feature Open-Heart (Display of escapement)
    10. Hacking Yes
    11. Manual Winding Yes
    12. Winding Direction Clockwise
    13. Power Reserve More than 41 Hours
    14. Hands Fitting Size H:150mm, M:88mm, S:20mm
    1. Movement x1
    2. Full length threaded stem x1
    3. Dummy stem & plastic crown x1
    1. To learn how to upgrade your movement, search YouTube: NH36 Movement Upgrade

Customer Reviews

Based on 11 reviews
Cameron (Melbourne, AU)

Regulated and accurate as claimed. Fast shipping and a pleasure to to business with, arrived with a personally written card - thank you again Adriel!

Billy R. (Fredericksburg, US)
Installed in built watch, running great!

Ordered this regulated movement with the 36mm Explorer style case, dial and hands. As of writing this review the movement is running great! Over 6 positions avg +3 sec/day with a total deviation (range) of 15 secs. avg Beat error of .3ms with total deviation of .6ms; as recorded via time grapher.

Sean Killins (Sidney, CA)
Using this mod part for: Aftermarket cases
Great movement

Again as always great customer service and quality products. Movement came very well timed. Cheers!

Wilfried Desmesures (Melun, FR)
Using this mod part for: Aftermarket case 36mm

Nice movement and fast delivery 👍

Deyron Infante (Houston, US)
Using this mod part for: Seiko

I fell in love with other this watch, to be honest the pictures on the site look stunning but nothing compares in person. This is my favorite watch now.. and shout out to adriel , my bro has the best service.

Mark Holterman (Sheffield, GB)
Using this mod part for: I’m building a custom bronze divers with no day or date complications.
Great Service

Very good personal service. This is my first purchase but it certainly won’t be my last!

Pat Hattori (Mechelen, BE)

Super fast delivery to Belgium! Couldn’t be happier!

Ramzi (Lubbock, US)
Using this mod part for: Unimatic U1
Seiko NH38

Prompt shipping. Nicely regulated movement. Superb customer service and communication. It was a delight to do business with Lucius Atelier.

Tom Devos (Ronse, BE)
Using this mod part for: Skx005
Great movement

This is a verry nice movement

Kirk S (Edmonton, CA)
Using this mod part for: Full build

OEM quality(because it’s a genuine Epson/Seiko movement). I’m glad that Adriel offers these, as they can be tough to source for no-date builds.