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.