Seiko (TMI) NH38 Automatic Movement - Open Heart - Regulated (0 to +8 secs/day) - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts

Seiko (TMI) NH38 Automatic Movement - Open Heart

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$190 SGD - $240 SGD

The open-heart showpiece.

Genuine Seiko NH38 automatic movement with an open-heart display, crown at 3 o'clock. A no-date, three-hand movement designed to pair with open-heart dials so the balance wheel is visible through a window in the dial. The escapement on show, from the front.

Two accuracy grades. One genuine Seiko caliber, QC-passed by TMI.
Pick Regulated for watchmaker-tuned precision, or Non-Regulated for Seiko factory spec. Every unit is a genuine Time Module Inc. movement, tested functional before it ships.

Watch it beat, from the front.
The NH38 is built so the oscillating balance wheel shows through an aperture in an open-heart dial, no display caseback needed. A live view of the escapement on the dial side.

Regulated or non-regulated.
Choose Regulated and a certified watchmaker tunes it to 0 to +8 seconds/day before it ships. Choose Non-Regulated for factory-default accuracy of -20 to +40 seconds/day per Seiko's spec. Same movement, your call on precision.

Hacking and hand-winding.
Both built in. The seconds hand stops when you pull the crown for precise time-setting, and you can manually wind it. The popular reason modders upgrade from older 7S26/7S36 calibers.

No date, clean three-hand.
A pure three-hand movement with no date complication, ideal for clean dials and open-heart faces. Ships with a full-length threaded stem and a dummy stem with plastic crown.

How the NH family compares

Caliber	Complication	Crown Position	Version
NH34	GMT + Date	3 or 4 o'clock	White
NH35	Date	3 or 4 o'clock	Black White
NH35	Date · 6 o'clock dial	3 or 4 o'clock	Black White
NH36	Day + Date	3 o'clock only	Black White
NH36	Day + Date	4 o'clock only	Black White
NH38 · THIS MOVEMENT	Open Heart (no date)	3 or 4 o'clock	View
NH70 / 71 / 72	Skeleton (no date)	3 or 4 o'clock	NH72

Most NH movements fit either a 3 or 4 o'clock crown — the stem threads either way and the date disc isn't affected. The NH36 is the exception: its day wheel is pre-aligned for one crown position, so pick the standard (3 o'clock) or the 4 o'clock version to match your case. Every caliber shares the same 24-jewel automatic platform, 21,600 vph beat rate, and 41+ hour power reserve. Click any version to go straight to that product.

For experienced modders only

Movement swapping is recommended only for individuals with the right skills and experience. Every movement passes Time Module Inc. (TMI) quality control before shipping and is guaranteed fully functional on arrival. Given the DIY nature of modding and Seiko's trade practices, movements cannot be returned once shipped. We are not responsible for damage incurred during fitting.

Specs
Compatibility
What's Included
How To Mod

1. Manufacturer Time Module Inc. (TMI)
2. Caliber NH38A
3. Movement Type Automatic, Mechanical
4. Hand Height Type M
5. Movement Diameter 27.40mm
6. Casing Diameter 29.36mm (with dial holding spacer)
7. Movement Height 5.32mm
8. Jewels 24 jewels
9. Beats Per Hour 21,600 vph (6 vibrations per second)
10. Additional Function None (3-hand, no date)
11. Hacking Yes
12. Manual Winding Yes
13. Winding Direction Clockwise
14. Power Reserve More than 41 hours
15. Accuracy (Regulated) 0 to +8 seconds/day
16. Accuracy (Non-Regulated) -20 to +40 seconds/day
17. Hands Fitting Size H: 1.5mm, M: 0.88mm, S: 0.2mm
Where this movement fits
1. Hand height Type M (standard) — confirm your case accepts Type M before fitting
2. Our cases All Ultra Thin Edition cases (TYPE M)
3. Dial 28.5mm Seiko Mod dials — no-date / open dials
4. Hands NH-series compatible
Pair the NH38 with an open-heart dial to use the cut-away view, or any no-date dial for a clean three-hander. Fits every Ultra Thin Edition case that takes a TYPE M movement.
1. 1x NH38 movement
2. 1x Full-length threaded stem
3. 1x Dummy stem with plastic crown
All photos showing movements fitted with dials, hands, or cases are for illustration only and are not included with the movement purchase.

What is the NH38 open heart, and which dial does it need?

The NH38 is a no-date, three-hand movement positioned so the balance wheel shows through an aperture in an open-heart dial — the escapement on view from the dial side, no display caseback needed. It needs an open-heart dial (or any no-date dial for a clean three-hander). The NH70, NH71 and NH72 also fit open-heart dials.

Will the NH38 fit a 3 or 4 o'clock crown case?

Yes, either. The NH38 has no date or day complication, so the crown stem threads at 3 or 4 o'clock freely. (Only the day+date NH36 is fixed to a specific crown position.)

What's the difference between Regulated and Non-Regulated?

Regulated movements are tuned by a certified watchmaker to 0 to +8 seconds per day before they ship. Non-Regulated movements run at Seiko's factory-default accuracy of -20 to +40 seconds per day. It's the same movement either way — Regulated just buys you tighter timekeeping out of the box.

Is this a Type M or Type L movement, and does it matter?

This is a Type M movement. Type M and Type L are Seiko's two factory hand-fitting heights; Type L sits about 0.4mm taller. Ultra Thin Edition cases have tight hand-to-sapphire clearance, so they take Type M only. Always confirm Type M before fitting.

Can I return a movement if my mod doesn't work out?

Movements can't be returned once shipped. Given the DIY nature of modding and Seiko's trade practices, all movement sales are final. Every unit passes TMI quality control and is guaranteed fully functional on arrival — but the fitting itself is at your own risk, so this movement is recommended for experienced modders only.