Introduction to the Seiko 6G28A

The Seiko 6G28A is an ultra-thin quartz analog movement developed in the 2000s, combining practical calendar complications with elegant design. Specifically engineered for dress watches, the 6G28A features a big date display and a retrograde day-of-week indicator, delivering an upscale appearance without adding mechanical bulk. It is known for its slim profile and is commonly found in Seiko’s refined dress collections, including JDM-only releases.

The 6G-series is often viewed as a successor to earlier 4J and 6F series movements but prioritizes aesthetic complexity over ultra-high accuracy, making it ideal for formal, fashion-forward timepieces.

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Technical Specifications

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Core Features

• Big date display, typically located at 12 o’clock

• Retrograde day-of-week hand, sweeping across a curved scale (often at 6 o’clock)

• Slim design, ideal for thin watch cases

• One-stepper motor controls time and calendar

• Designed for affordable elegance, with premium-style complications

The 6G28A offers visual sophistication similar to mechanical calendar watches, but with the maintenance ease of quartz.

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Setting Instructions

Crown Positions

• Turn clockwise in Position 1: Adjusts big date

• Turn counterclockwise in Position 1: Adjusts day-of-week (retrograde)

• Position 2: Time setting (hour and minute only; seconds hand not present)

The calendar does not self-adjust for short months or leap years, so manual correction is required at the end of 30-day months and in February.

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Big Date Display

The big date complication features:

• Two separate discs: one for the tens digit, one for the units

• Positioned together to create a large, legible double-digit date window

• Advances once per 24-hour cycle, usually around midnight

• Quickset enabled for easy correction

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Retrograde Day Display

• Day of the week is shown by a sweeping hand that moves across a curved scale

• After Sunday, the hand jumps back to Monday, creating a visually interesting movement

• Controlled by a cam and spring mechanism tied to the calendar geartrain

• Adjustment is manual via the crown

If the hand becomes misaligned, it can be reset by rotating backward through the days.

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Battery and Power Details

Battery Type

• SR621SW (Seiko 364)

• Voltage: 1.55V

• Lifespan: ~2 years

Battery Replacement Procedure

1. Open the case back carefully

2. Remove old battery using plastic tweezers

3. Insert new battery, confirming polarity

4. No reset required — the IC resumes operation upon power restoration

5. Set time, day, and date manually after battery change

6. Close case securely and pressure test if applicable

Always inspect the gasket for wear and replace if necessary during service.

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Maintenance and Servicing

The 6G28A is a non-jeweled, modular movement designed for replacement, not repair. However, routine battery service and hand/crown adjustments are possible.

Common Service Items

• Battery replacement

• Hand reset or realignment

• Day/date gear cleaning (if jump is sluggish)

• Replacement of full movement in case of failure

Because of its complexity and slimness, the calendar display must be realigned carefully during reinstallation.

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Troubleshooting Guide

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Watches Featuring the 6G28A

The 6G28A is found in:

• Seiko Premier and Brightz dress watches

• JDM-exclusive Seiko models emphasizing calendar complexity

• Models with 12 o'clock big date windows and 6 o'clock retrograde subdials

• Elegant timepieces with stainless steel or gold-plated cases and leather straps

These watches were designed for the style-conscious wearer who wanted traditional complications in a slim quartz format.

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Conclusion

The Seiko 6G28A delivers a sophisticated calendar layout in a slim, reliable quartz movement, offering:

• Visually striking big date and retrograde day

• Slim case compatibility

• Easy operation and maintenance

• Reliable ±20 seconds/month accuracy

While not designed for service like Seiko’s luxury 6F-series, the 6G28A remains a refined and elegant choice for those seeking timeless aesthetics with quartz simplicity.

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