The Seiko 7A38A is a legendary quartz chronograph movement and the direct successor to the groundbreaking 7A28A—the world’s first analog quartz chronograph. Introduced in 1983, the 7A38A brought several enhancements to the table, including a day/date complication, while retaining the same robust and fully analog design that made the 7A28A iconic.

This caliber belongs to Seiko’s 7Axx series, which set a new standard for quartz chronographs. With its jewel bearings, metal gear trains, and independent stepper motors for each chronograph function, the 7A38A was built not just for accuracy—but for longevity and serviceability. Today, it is highly collectible and considered one of the finest quartz chronograph movements ever made.

Movement Overview

• Caliber: Seiko 7A38A

• Movement Type: Quartz (analog chronograph)

• Jewels: 15

• Battery: Seiko 943 / SR927W (1.55V silver oxide)

• Accuracy: ±10 to ±15 seconds per month

• Battery Life: Approx. 2–3 years

• Display: Full analog, four registers

• Functions: Chronograph, day-date, timekeeping

Dial Layout

The 7A38A adds useful calendar features while maintaining a symmetrical chronograph layout. Standard configuration includes:

• Central hour and minute hands

• Chronograph sweep seconds hand (center)

• 1/10-second counter at 3 o’clock

• 60-minute totalizer at 9 o’clock

• Continuous seconds at 6 o’clock

• Day and date window at 12 o’clock

The day and date display is a standout feature, offering either bilingual days (e.g., English/Spanish or English/French) depending on the market. Both can be quickset independently.

Chronograph Operation

The chronograph is fully analog, controlled by a trio of stepper motors and offering precise elapsed time measurements up to 60 minutes, with 1/10-second accuracy.

Operation:

• Start/Stop: Upper right button (Button A)

• Reset: Lower right button (Button B)

• Chronograph hand calibration: Left-side pushers (at 8 and 10 o’clock)

The 1/10-second subdial moves only when the chronograph is stopped, jumping to the precise recorded time. This is an intentional energy-saving feature.

Day-Date Adjustment

The crown has three positions:

• Pushed in: Normal operation

• First click:

  • Rotate clockwise to change the date

  • Rotate counterclockwise to change the day

• Second click: Set the time (with hacking seconds)

The quickset mechanism allows fast adjustment, but always avoid changing the calendar during the danger zone (around 9 PM to 3 AM), which can damage the date-change gears.

Battery and End-of-Life Behavior

• Battery type: SR927W

• Typical lifespan: 2–3 years

• Low battery behavior: No specific EOL (End of Life) indicator. Malfunctions such as slow or erratic chronograph hands may indicate a depleted cell.

Battery replacement:

1. Remove the case back using a case opener.

2. Carefully extract the battery with non-metallic tweezers.

3. Install the new SR927W cell.

4. To reset the integrated circuit (IC), short the AC contact to the battery + terminal with metal tweezers.

5. Re-calibrate chronograph hands if needed using the left-side pushers.

Always replace the gasket and ensure the case is sealed properly, especially on water-resistant models.

Key Features

Collectibility and Usage

Watches housing the 7A38A movement come in a wide variety of designs—from dress chronographs to robust sports models. Some were used in military contracts, while others featured gold-tone or stainless steel cases aimed at professionals. Notable variants include:

• 7A38-7190 with tachymeter bezel

• 7A38-7020 with integrated bracelet design

• 7A38-7070 in a sporty two-tone configuration

Thanks to its bulletproof construction, watches powered by the 7A38A are often still running today, decades later, with minimal maintenance.

Final Thoughts

The Seiko 7A38A is more than just a quartz movement—it's a mechanical soul in an electronic body. With its jeweled movement, full metal gears, and analog functionality, it remains one of the most respected quartz chronographs ever produced.

If you’re lucky enough to own a 7A38A-powered watch, you’re wearing a true milestone in horology—a machine built not just for accuracy, but for generations.