The Seiko S123A is a hybrid analog-digital quartz movement known for its blend of traditional analog hands and a multifunction LCD display. Developed for sport, aviation, and tactical watches, the S123A offers a robust suite of features including chronograph, alarm, calendar, and dual time—all within a reliable and compact movement.

This caliber represents Seiko’s expertise in creating watches that are both visually classic and functionally modern. It's often found in Seiko models aimed at active users who want quick analog legibility with the utility of digital functions.

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Overview

The Seiko S123A belongs to Seiko’s family of "ana-digi" movements, combining mechanical analog hands with a digital display in a single module. It enhances readability and function without increasing complexity for the user. The S123A improves on older generations by offering better digital visibility, a more refined user interface, and excellent battery efficiency despite its multifunction layout.

It is especially well-suited for users such as pilots, athletes, and global travelers, thanks to its combination of analog precision and digital features.

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Key Features

• Analog Timekeeping: Hour and minute hands powered by a quartz-controlled stepper motor.

• Digital Display (LCD): Compact screen offering dynamic readouts.

• Chronograph (Stopwatch): Measures elapsed time up to 100 minutes with 1/100-second accuracy.

• Daily Alarm: Single programmable alarm.

• Dual Time Zone: Independent digital second time display.

• Full Auto Calendar: Pre-programmed (often up to 2049 or later).

• Backlight: LED or EL panel for nighttime viewing.

• 12/24-Hour Format Toggle: View digital time in standard or military format.

• Battery Life Indicator: Low battery alert on digital screen.

Each of these functions is operated through pushers located around the case, often labeled A/B/C/D depending on the watch model.

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Technical Specifications

• Caliber: Seiko S123A

• Movement Type: Quartz (analog-digital hybrid)

• Display: Analog hands + digital LCD

• Battery Type: SR927W (1.55V silver oxide)

• Battery Life: Approx. 2–3 years (depending on backlight/alarm usage)

• Accuracy: ±15 seconds per month

• Jewel Count: 0

• Dimensions:

  • Diameter: Approx. 30 mm

  • Thickness: Approx. 6.0 mm

• Hand Hole Sizes:

  • Hour: 1.10 mm

  • Minute: 0.65 mm

  • (No analog seconds hand—digital seconds used for precision)

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Operation & Button Functions

Typical button layout includes:

• A (Top Left): Change mode (Time → Chrono → Alarm → Dual Time → Calendar)

• B (Top Right): Start/Stop or toggle (used in chrono and alarm modes)

• C (Bottom Left): Set or reset values

• D (Bottom Right): Backlight or alternate function toggle

The analog and digital time can usually be set independently, although some models synchronize both automatically.

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Servicing Guidelines

Battery Replacement

• Use non-metallic tweezers to remove the old SR927W battery.

• Always perform an AC reset by bridging the AC contact and battery edge with metal tweezers. This initializes the digital module.

• After replacement, verify that the backlight, alarm, and LCD display are functioning properly.

Analog Hand Calibration

• Analog hands are adjusted via the crown.

• Ensure the analog and digital times are synced if the model supports it. Otherwise, adjust independently.

LCD Check

• After battery installation, check for missing LCD segments.

• Replace the entire module if LCD damage or leakage is detected (individual screens are not user-serviceable).

Case Maintenance

• Replace gaskets and test water resistance after servicing.

• Clean pushers and spring contacts to maintain digital responsiveness.

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Common Issues

• Analog Hands Out of Sync: May occur after a battery change or AC reset. Manually adjust the hands via the crown.

• Blank or Fading Display: Usually caused by a low battery or failed reset. Replace battery and perform AC reset.

• Backlight Not Working: Could be due to battery drain or EL panel failure (non-replaceable).

• Unresponsive Buttons: Often due to moisture ingress or pusher corrosion—clean and test contacts.

• Calendar or Dual Time Incorrect: Reconfigure via mode selection and adjust settings manually.

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Conclusion

The Seiko S123A is a durable and functional hybrid quartz movement that blends analog elegance with digital flexibility. It offers a feature-rich platform in a compact module that is easy to service and intuitive to use. Perfect for tool watches, travel watches, or sporty daily wearers, the S123A reflects Seiko’s enduring commitment to practical innovation in quartz technology. Whether for the enthusiast or the everyday user, it delivers dependable performance and versatility in one well-crafted package.

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