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This is a genuine Seiko (SII) first reduction wheel (part #0511010), an original Japanese-made component for the popular NH35, NH36, NH37, NH38, and NH39 automatic movements. As a critical part of the automatic winding system, this gear transfers rotational energy from the oscillating weight to the mainspring barrel, ensuring efficient power generation.
This brand new original part is essential for watchmakers restoring proper automatic winding function when the original wheel becomes worn or damaged.
Sapphire Crystal – Mohs 9, highly scratch-resistant and optically clear.
Pan-Shaped Domed Profile – Faithfully replicates the iconic aviation‑instrument curved crystal.
Precise Dimensions – 35.0mm diameter, 3.4mm height – exact fit for the 40mm Pilot case.
Generic Aftermarket – Non-original but manufactured to OEM specs for direct replacement.
Cost-Effective – Affordable alternative for repair or restoration.
| Parameter | Details |
|---|---|
| Compatible Model | Zenith Pilot Type 20 Extra Special 11.1940.679 |
| Type | Generic aftermarket |
| Material | Synthetic sapphire |
| Shape | Pan-shaped (domed) |
| Diameter | 35.0 mm |
| Height | 3.4 mm |
Zenith Pilot Type 20 Extra Special 11.1940.679 (40mm steel case, vintage pilot watch)
Other Pilot series models using the same 35.0mm domed crystal (verify original size)
Replacement of damaged, deeply scratched, or aged original crystals
Maintaining the unique aviation‑instrument look
1. Is this a genuine Zenith crystal?
No. It is a generic aftermarket replacement, not original, but matches the 11.1940.679 dimensions.
2. Does this crystal fit other Pilot models (e.g., 29.2430.679)?
Different Pilot references have different case and crystal sizes (e.g., 45mm cases use larger crystals). Measure your original crystal diameter and height – should be 35mm/3.4mm.
3. What should I pay attention to during installation?
The pan-shaped crystal has a specific orientation – dome facing outward. Use a new gasket and UV adhesive, press evenly with a crystal press. Professional installation is recommended.
4. Will the original water resistance be maintained?
Pilot Type 20 is typically 50-100m water resistant. Proper installation with a new gasket can restore similar resistance. A water resistance test is advised.
5. Is a gasket included?
Usually not. The sealing gasket must be purchased separately. Confirm with the seller.
Fast worldwide shipping within 3 business days.
Competitive pricing on Seiko/Hattori calibers.
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