Seiko 4502A - Parts List
Seiko 4502A – Technical Guide
General Overview
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Caliber: Seiko 4502A
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Type: Manual-wind mechanical movement
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Manufacturer: Daini Seikosha (Seiko Instruments Inc.)
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Production Period: Late 1960s to early 1970s
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Movement Family: 45-series
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Primary Use: King Seiko Chronometer models
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Notable Feature: High-beat accuracy with date and hacking seconds
Technical Specifications
| Feature | Specification |
|---|---|
| Winding System | Manual winding only |
| Jewels | 25 |
| Frequency | 36,000 A/h (10 beats per second) |
| Power Reserve | Approx. 40 hours |
| Shock Protection | Diashock (balance staff) |
| Hacking Seconds | Yes |
| Calendar | Date (non-quickset, instantaneous jump) |
| Diameter | ~26 mm |
| Thickness | ~4.5 mm |
| Finishing | Brushed plates, polished screws |
Functional Description
The Seiko 4502A is an advanced high-beat, hand-wound movement with hacking seconds and a date complication, used in King Seiko 45KS Chronometer models. Designed for maximum precision, it represents Seiko’s pursuit of world-class mechanical watchmaking in the late 1960s.
Crown Operation
| Position | Function |
|---|---|
| 0 | Manual winding |
| 1 | Time setting (hacks) |
The date does not have quickset. It advances automatically at midnight and can be manually changed by cycling the hands past 12 AM repeatedly.
Calendar System
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Date display: 1–31 numeric window at 3 o'clock
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Instantaneous date change around midnight
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No quickset — adjust by turning hands past midnight
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Date mechanism uses a jump system powered by tensioned levers and springs
Watch Models Using 4502A
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King Seiko 45-7001 Chronometer
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King Seiko 45-8010 / 8011 Chronometer
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Case sizes typically 36–37 mm
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Dials often marked “Chronometer Officially Certified”
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Medallion casebacks with the King Seiko shield emblem
Performance Benchmarks
| Metric | Post-Service Target |
|---|---|
| Accuracy | ±5 to ±10 seconds/day |
| Amplitude | 250°–280° (fully wound, dial up) |
| Beat Error | ≤ 0.3 ms |
The 4502A was built to chronometer standards and can still achieve excellent timekeeping when properly serviced.
Disassembly and Servicing Notes
| Component | Watchmaker Notes |
|---|---|
| Balance Assembly | Fine pivots — handle with care. Includes hacking lever mechanism |
| Date Mechanism | Instant-jump system — preloads energy before midnight |
| Barrel | Replace mainspring on service; key to maintaining amplitude |
| Train Wheels | High-beat gear teeth wear faster — inspect closely |
| Keyless Works | Hacking lever interacts with clutch; check for smooth operation |
Because of the 36,000 bph rate, cleanliness and lubrication are critical to maintain accuracy and longevity.
Lubrication Chart
| Location | Lubricant |
|---|---|
| Train Wheel Pivots | Moebius 9010 |
| Escape Wheel Teeth | Moebius 941 |
| Pallet Stones | Moebius 941 |
| Balance Cap Jewels | Moebius 9010 |
| Barrel Arbor & Bridle | Moebius 8200 |
| Keyless Works & Hack Lever | Molykote DX or HP1300 |
Use light, controlled oiling throughout. Over-lubrication can dampen amplitude in high-frequency movements.
Common Issues and Fixes
| Problem | Likely Cause | Recommended Solution |
|---|---|---|
| Low amplitude | Dry pivots or old mainspring | Clean and relubricate; replace spring |
| Hacking lever sticks | Dirty hack lever or spring tension | Disassemble, clean, and re-tension |
| Date jumps late | Weak jumper spring or misaligned wheel | Adjust or replace jumper |
| Irregular timing | Worn escape or train pivots | Inspect and replace worn parts |
Collectibility and Value
The Seiko 4502A is one of the most sought-after hand-wound Seiko calibers, especially when housed in Chronometer-certified King Seiko cases.
| Condition | Approximate Value (watch) |
|---|---|
| Worn, unrestored | $600–$900 |
| Serviced, clean | $1,000–$1,400 |
| Mint or boxed | $1,500–$2,000+ |
Loose movements or parts are rare due to collector demand and limited production.
Conclusion
The Seiko 4502A is a masterpiece of mechanical engineering from Seiko’s golden age. With its hacking seconds, high-beat accuracy, and clean design, it exemplifies everything collectors value in a King Seiko movement. It remains one of the finest hand-wound calibers Seiko has ever produced and is a joy to service, regulate, and wear.
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