Seiko 10C - Parts List
Seiko 10C – Technical Guide (High Quality)
The Seiko 10C is a vintage mechanical hand-winding movement designed and produced in the early 1950s. It belongs to Seiko’s early post-war movement development era and was used in the Seikosha-branded wristwatches, before the full adoption of the Seiko name in branding. The 10C was compact, reliable, and purpose-built for small men’s or unisex wristwatches during Japan’s transition into precision mechanical watch manufacturing.
1. Technical Specifications
| Feature | Details |
|---|---|
| Caliber Number | Seiko 10C (also marked Seikosha) |
| Movement Type | Mechanical – Hand-winding |
| Functions | Hour, Minute, Central Seconds |
| Jewels | 15 or 17 (depending on variant) |
| Beat Rate | 18,000 vibrations/hour (5 beats/sec) |
| Power Reserve | ~38–42 hours |
| Manual Winding | Yes |
| Automatic Winding | No |
| Hacking Seconds | No |
| Calendar | None |
| Diameter | ~23.0 mm (~10 ligne) |
| Height | ~4.3 mm |
| Shock Protection | Typically none or early Seikosha spring types |
2. Key Features
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Simple 3-hand layout (hour, minute, center seconds)
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No date or complications – very clean mechanical layout
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Used in Seikosha and early Seiko-branded dress watches
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Manual winding only, solid stem and crown system
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Constructed with brass main plate and bridges
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Engraved or stamped bridge with “Seikosha 10C” marking
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Reliable and durable, designed for ease of maintenance
The 10C was one of the earliest fully in-house calibers made by Seikosha, forming a foundation for Seiko’s future precision movements.
3. Winding and Time Setting
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Wind the crown clockwise daily (approx. 15–20 full turns)
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Pull the crown to its only position to set the time
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There is no stop-seconds (non-hacking)
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No quickset date (no date feature)
4. Movement Architecture
Dial Side:
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Cannon pinion, hour and minute wheels
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Time-setting clutch with basic yoke system
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No calendar or additional complications
Train Side:
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Barrel and mainspring
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Center wheel, third wheel, fourth wheel, escape wheel
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Pallet fork and balance wheel
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Plain regulator arm, swan-neck not typically present
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Balance wheel with Breguet hairspring (early models)
The overall layout is service-friendly, with minimal layers and easily accessible pivots.
5. Servicing Guidelines
| Component | Service Notes |
|---|---|
| Mainspring | Inspect for stickiness or set spring; replace if needed |
| Lubrication | Use fine-grade watch oil on train and escapement pivots |
| Balance assembly | May be fragile; avoid over-handling |
| Cleaning | Manual or ultrasonic cleaning required for vintage oils |
| Timing regulation | Basic regulator with limited adjustment range |
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