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Seiko 4R38 / NH38 Parts
The 4R38 and NH38 movements are both reliable automatic movements produced by Seiko Instruments Inc. (SII) and are nearly identical in terms of technical specifications. The differences lie mainly in branding, calibration, and target markets. Here’s a detailed comparison:
Similarities
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Mechanical Features:
- Both are automatic movements with manual winding and hacking (second-hand stop when setting the time).
- They share the same technical specifications:
- Beats per hour (BPH): 21,600 (6 ticks per second).
- Power reserve: Approximately 41 hours.
- Number of jewels: 24.
- Neither has a date complication, making them ideal for watches with "clean dials" or minimalistic designs.
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Design and Durability:
- Both movements are robust and reliable, designed for long-term use with minimal maintenance.
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Functionality:
- Both are functionally identical, with no date function and hacking/manual winding capabilities.
Differences
| Aspect | 4R38 | NH38 |
|---|---|---|
| Branding | Exclusively used in Seiko watches, often branded with "Seiko". | Unbranded or marked with "SII", designed for third-party manufacturers. |
| Purpose | Designed solely for Seiko watches. | Sold to external manufacturers and microbrands. |
| Calibration | Pre-calibrated by Seiko for their watches, often with stricter tolerances. | Usually not pre-calibrated; regulation is left to the manufacturer. |
| Availability | Only available as part of Seiko watches. | Widely available for purchase as a standalone movement through aftermarket suppliers. |
| Rotor Decoration | Branded "Seiko" and may include decorative finishes. | Typically unbranded or marked with "SII"; customizable rotors are often added by third-party brands. |
| Price | Included in Seiko watches; not sold separately. | More affordable and widely available in the aftermarket. |
Use Cases
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4R38:
- Found in Seiko watches that emphasize a clean and minimalistic aesthetic, such as dress watches or skeleton models.
- Not available for independent watchmakers or aftermarket projects.
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NH38:
- Commonly used by microbrands and independent watchmakers for minimalist designs without a date complication.
- A popular choice for custom watches or aftermarket modifications due to its availability and affordability.
Which One Should You Choose?
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4R38:
- Ideal for those seeking authenticity in Seiko watches or needing an original replacement for a Seiko model.
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NH38:
- Best for independent projects, microbrands, or aftermarket watchmaking where a reliable, clean-dial movement is needed.
Conclusion
The 4R38 and NH38 are mechanically identical but cater to different markets. The 4R38 is reserved for Seiko's in-house watches and carries their branding, while the NH38 is unbranded and widely used by third-party manufacturers for minimalist or clean-dial designs.
