The Seiko 8620A is a precise and robust quartz analog movement designed to deliver reliable timekeeping and a convenient date function. Produced mainly during the 1980s and 1990s, the 8620A is a classic Seiko caliber that combines accuracy, simplicity, and durability, making it a popular choice for everyday watches. Known for its stable performance and low maintenance, the 8620A remains a respected movement in the quartz watch world.

Technical Specifications

• Caliber Number: 8620A

• Movement Type: Quartz (Analog)

• Display:

  • Hour, minute, and seconds hands

  • Date window, typically located 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 operation

  • Position 1: Date adjustment

  • Position 2: Time adjustment

Key Features

Accurate Timekeeping

Equipped with a quartz oscillator, the 8620A provides consistent and accurate timekeeping with a typical accuracy of ±20 seconds per month, making it suitable for reliable daily wear.

Date Display

A date complication is incorporated in the movement and displayed through a window, typically positioned at 3 o’clock, allowing users to easily read and adjust the date.

Efficient Battery Life

Powered by an SR927W silver oxide battery, the movement offers efficient power consumption, enabling a battery life ranging from two to three years under normal usage.

Operating Instructions

Time Setting

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

2. Rotate the crown clockwise or counterclockwise to adjust the hour and minute hands.

3. Push the crown back to Position 0 to resume regular 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 manually between 9 PM and 2 AM to prevent damage to the date mechanism.

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

Battery Replacement and Maintenance

• Use an SR927W silver oxide battery for replacement.

• Battery life generally lasts 2 to 3 years depending on conditions and usage.

• It is advisable to have battery replacement performed by a professional to maintain water resistance and avoid damage.

• No reset is usually necessary after battery change, though time and date should be checked and adjusted as needed.

Maintenance Recommendations

• The quartz electronic movement requires no lubrication or mechanical servicing.

• Avoid exposure to strong magnetic fields, impacts, and temperature extremes to maintain accuracy.

• Clean the watch regularly, particularly after exposure to moisture or dirt.

• Water-resistant models should be tested periodically to ensure the integrity of seals.

Watches Featuring the 8620A

The 8620A caliber was used in:

• Various Seiko quartz watches during the 1980s and 1990s.

• Models that emphasize straightforward timekeeping and date functions.

• Timepieces designed for everyday reliability and classic styling.

Summary Table

Conclusion

The Seiko 8620A quartz movement is a reliable and accurate caliber offering essential analog timekeeping paired with a convenient date display. Its efficiency, durability, and low maintenance requirements make it a trusted choice for everyday watches. The 8620A reflects Seiko’s longstanding reputation for producing high-quality quartz movements that combine precision with simplicity and durability.