Automatic (No Date / Open-Heart)

A reliable Japanese automatic movement designed without a date complication, making it ideal for clean no-date dials and open-heart watches. The NH38 offers the same trusted reliability as the NH35 while eliminating the unused date mechanism for a cleaner aesthetic.

The TMI NH38 is an automatic mechanical movement developed by TMI (Time Module Inc., part of the Seiko Group). Built on the trusted NH series platform, it features automatic winding, manual winding, and hacking seconds, but does not include a date function, making it a popular choice for minimalist and open-heart timepieces.


Specification

Details

Manufacturer

TMI (Seiko Group)

Caliber

NH38

Movement Type

Automatic with Manual Winding

Functions

Hours, Minutes, Seconds

Jewels

24 Jewels

Beat Rate

21,600 BPH (3 Hz)

Power Reserve

Approx. 41 Hours

Diameter

27.40 mm

Height

5.32 mm

Accuracy

-20 / +40 seconds per day

Hacking Seconds

Yes

Country of Origin

Japan or Malaysia

Operating Instructions

Automatic Winding

The NH38 automatically winds itself through the natural movement of your wrist while worn.

Manual Winding

If the watch has stopped:

  • Turn the crown clockwise approximately 55 times to fully wind the mainspring.

  • The watch will continue winding automatically while being worn.

Setting the Time

  1. Pull the crown to the second click.

  2. Turn the crown until the correct time is displayed.

  3. The second hand stops while setting the time for precise synchronization.

  4. Push the crown back to the normal position.

Note: The NH38 does not feature a date complication, so there is no date-setting position.

Care & Maintenance

  • Wear the watch regularly to keep the movement wound.

  • If not worn for several days, manually wind before use.

  • Avoid strong magnetic fields and severe impacts.

  • Keep the crown fully pushed in (or screwed down if applicable).

  • Professional servicing is recommended every 5–7 years, depending on usage and environmental conditions.

Why Choose the NH38?

  • Genuine Japanese automatic movement

  • No-date design for a clean dial appearance

  • Ideal for open-heart and minimalist watches

  • Manual winding capability

  • Hacking seconds for precise time setting

  • Approximately 41-hour power reserve

  • Durable, reliable, and easy to service

The TMI NH38 delivers the same proven reliability as the NH35 while eliminating the date complication, making it the perfect movement for open-heart and no-date watches where a clean, symmetrical dial design is desired.