Seiko 2107A – Technical Guide (High Quality)

The Seiko 2107A is a manual-winding mechanical movement introduced in the 1960s, designed primarily for ladies’ wristwatches. This caliber features a precise and compact two-hand layout (hour and minute), optimized for slim, elegant cases while maintaining reliability and ease of service. The 2107A embodies Seiko’s commitment to quality craftsmanship in smaller mechanical movements tailored for women’s timepieces.

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1. Technical Specifications

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2. Key Features

• Two-hand time display focusing on hour and minute functions

• Compact and slim movement size ideal for delicate ladies’ watches

• 17-jewel construction for enhanced durability and smooth operation

• Diashock balance staff protection improving shock resistance

• Reliable manual winding mechanism with consistent power delivery

• Service-friendly architecture facilitating maintenance and repairs

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3. Operating Instructions

Manual Winding:

• Wind the crown clockwise daily until firm resistance is felt; avoid overwinding

• Power reserve typically lasts about 40 hours when fully wound

Time Setting:

• Pull the crown out to the time-setting position

• Rotate to adjust hour and minute hands

• Push the crown back in to resume normal operation

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4. Movement Architecture

Dial Side:

• Hour and minute wheels with cannon pinion

• Keyless works with sliding pinion and clutch wheel for setting

Gear Train Side:

• Mainspring barrel equipped with ratchet and click spring

• Gear train including center, third, and escape wheels

• Pallet fork and balance wheel with flat hairspring

• Regulator lever for fine adjustment of timing

• Diashock protection system on balance pivots

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5. Service Recommendations

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6. Common Issues & Solutions

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7. Applications

The Seiko 2107A movement was commonly used in:

• Ladies’ wristwatches with slim and elegant cases (around 18–22 mm diameter)

• Polished steel or gold-plated cases

• Minimalist dials lacking seconds or date complications

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8. Historical Context

The 2107A exemplifies Seiko’s focus during the 1960s on:

• Developing precise, compact mechanical calibers for women’s watches

• Balancing durability with slim form factors

• Contributing to Seiko’s reputation for reliable and elegant mechanical movements

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9. Conclusion

The Seiko 2107A is a dependable and elegant manual-winding caliber tailored for vintage ladies’ wristwatches. Its minimalist two-hand design, slim profile, and robust mechanical construction make it a favored movement for collectors and watchmakers. With proper maintenance, the 2107A continues to offer graceful and accurate timekeeping that reflects Seiko’s mid-20th century watchmaking expertise.

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