The Seiko 8620A is a dependable and precise quartz analog movement designed to provide accurate timekeeping alongside a practical date function. Produced primarily during the 1980s and 1990s, the 8620A reflects Seiko’s expertise in crafting robust quartz calibers suited for everyday wristwatches. Its simple yet efficient design offers reliability, low maintenance, and consistent performance, making it a favored choice for many Seiko models.

Technical Specifications

• Caliber Number: 8620A

• Movement Type: Quartz (Analog)

• Display:

  • Hours, minutes, and seconds hands

  • Date window typically at 3 o’clock

• Accuracy: Approximately ±20 seconds per month

• Battery Type: SR927W (1.55V silver oxide)

• Battery Life: Around 2 to 3 years

• Jewels: None (electronic quartz movement)

• Crown Positions:

  • Position 0: Normal running

  • Position 1: Date adjustment

  • Position 2: Time adjustment

Key Features

Reliable Timekeeping

Driven by a quartz oscillator, the 8620A provides stable and accurate timekeeping, generally maintaining an accuracy of ±20 seconds per month, sufficient for daily use.

Date Display

Equipped with a date complication, the movement displays the date in a window, most commonly located at the 3 o’clock position, allowing for quick and easy date reference.

Efficient Power Consumption

The 8620A uses an SR927W silver oxide battery, which typically lasts between two and three years, minimizing the need for frequent battery changes.

Operating Instructions

Time Setting

1. Pull the crown to the second click (Position 2).

2. Rotate the crown clockwise or counterclockwise to set the desired time.

3. Push the crown back to Position 0 to resume normal operation.

Date Setting

1. Pull the crown to the first click (Position 1).

2. Rotate the crown clockwise to advance the date.

3. Avoid adjusting the date between 9 PM and 2 AM to prevent damage to the date-change mechanism.

4. Push the crown back to Position 0 after adjustment.

Battery Replacement and Maintenance

• Replace the battery with an SR927W silver oxide battery when necessary.

• Battery life typically spans 2 to 3 years, depending on usage.

• Professional replacement is recommended to maintain water resistance and proper sealing.

• No special reset is usually required after battery replacement, but the time and date should be verified.

Maintenance Recommendations

• The movement requires no mechanical lubrication as it is fully electronic.

• Avoid strong magnetic fields, shocks, and temperature extremes to preserve accuracy and longevity.

• Clean the watch regularly to maintain optimal appearance and function.

• Water-resistant models should be pressure tested periodically.

Watches Featuring the 8620A

The 8620A has been installed in:

• Seiko quartz analog watches from the 1980s and 1990s.

• Models emphasizing practical time and date display without extra complications.

• Watches designed for everyday durability and classic styling.

Summary Table

Conclusion

The Seiko 8620A is a dependable quartz movement that delivers precise analog timekeeping and an easy-to-use date function. Its efficient battery use, straightforward design, and reliable performance make it an excellent choice for everyday watches. The 8620A exemplifies Seiko’s dedication to quality and accuracy in quartz watch movements, offering users lasting value and minimal maintenance.