Seiko 8B43

Seiko Caliber 8B43

Seiko 8B43

Brand Seiko
Caliber Number 8B43
Movement Type Solar Powered (Quartz)
Jewels Unkown
Crystal Oscillator Frequency
32,768 Hz (cycles per second)
Power Reserve 9 months on full charge
Radio Signal JJY-LF
Functions Automatic radio wave Atomic Clock time setting, date, day
Country of Manufacture Japan
Known Models SAGA081, SAGA083

The Seiko caliber 8B43 is a Radio Wave Control Solar Powered movement found in JDM Brightz models. It appears that this caliber is not found in watches meant for the North American market.

Seiko claims accuracy of a monthly rate of +/- 15 seconds in normal conditions.

Several of the Seiko radio-controlled calibers will not sync in the US, but the 8B43 may not have any issues with syncing. However, it’s important to note that calibers meant for the worldwide market include user manuals that show a world map, whilst the caliber 8B43 only shows a map of Japan. Please comment below with your experiences.

Based on similar calibers, we know the following:

  • No battery change required
  • Lasts for up to 9 months after a full charge
  • Equipped with overcharging prevention and power saving functions
  • Automatic hand position adjustment function

How it works:

The Cesium Atomic Clock transmitting station sends a radio signal out with the current time information. The radio controlled watch received the radio signal through an antenna inside the watch. The watch analyzes the information received and then automatically sets itself to display the current time, day, and date.

The Seiko Astron models feature similar functionality, check out the caliber 7X52 here.


The official manual for this movement is available in Japanese and English starting on page 88. A manual for the next closest caliber (8B63) can be found in English here.


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