Seiko 7S26 / NH23 Movement Parts

The NH23 and the 7S26 movements are quite similar because they are both simple, reliable automatic movements produced by Seiko Instruments Inc. (SII). However, the NH23 is a more modern version designed for external manufacturers (e.g., microbrands), while the 7S26 was exclusively used in Seiko watches. Here are the key differences and similarities:

Similarities

Mechanical Base:
- Both are automatic movements without manual winding or hacking features.
- They share similar specifications:
  - Beats per hour (BPH): 21,600.
  - Power reserve: Approximately 40 hours.
  - Number of jewels: 21.
Use Case:
- Both are designed for entry-level, affordable watches.
- Renowned for their simplicity, reliability, and low maintenance.
Day and Date Complication:
- Both movements feature a day-date function, often with the day displayed in two languages (depending on the watch).

Differences

Feature	NH23	7S26
Purpose	Designed for external manufacturers (microbrands, aftermarket).	Exclusive to Seiko watches.
Production	Modern version, still in production.	Discontinued, no longer produced.
Calibration	Basic settings, often adjusted by the manufacturer.	Pre-calibrated by Seiko for their watches.
Parts Availability	Easily available in aftermarket.	Harder to find due to discontinued status.
Rotor Branding	Unbranded or marked with "SII".	Seiko-branded.
Compatibility	Compatible with a wide range of watch cases.	Specific to Seiko watch cases.

Advantages of the NH23 Over the 7S26

Availability:
- The NH23 is still in production and readily available from aftermarket and wholesale channels.
- The 7S26 has been discontinued, making it harder to source complete movements or spare parts.
Flexibility:
- The NH23 is widely used by microbrands and external manufacturers, offering greater versatility.
- The 7S26 was limited to Seiko watches, making it less adaptable for aftermarket use.
Modernized Production:
- While functionally similar, the NH23 benefits from more modern production techniques, potentially offering improved consistency and reliability.

When to Choose Which?

NH23:
- Best for new watches, microbrand projects, or aftermarket replacements.
- Ideal when you need a modern, widely available movement.
7S26:
- Only relevant for repairing Seiko watches or vintage projects where using an original Seiko movement is essential.

Conclusion

The NH23 is essentially a modern, aftermarket-oriented version of the 7S26. The primary difference lies in availability and target audience: the NH23 is versatile and designed for broader applications, while the 7S26 is a classic Seiko movement that was exclusive to Seiko watches.

Seiko 7S26 / NH23 Parts