Seiko Caliber 7B72

Manufacturer	Seiko
Caliber Number	7B72
Movement Type	Solar-powered, radio-controlled, quartz
Display	Analog
Jewel Count	0
Frequency	32,768 Hz
Capacitor Part #	3023 24M, 302324M (unconfirmed!)
Power Reserve	~9 months on a full charge
Integrated Circuit	2 piece IC – Oscillator, frequency divider, drive/reception circuit
Driving System	Step motor
Hand Count	3
Functions	Central hours; central minutes; central seconds; date at 3:00
Other Features	Radio signal reception for automatic time setting
Hacking Seconds?	Yes
Country of Manufacture	Made in Japan
Known Models	Seiko Astron (Ref: SBXY029, SBXY031, SBXY033), Seiko Modellista (Ref: SBTM331) (Add your watch to the comments below…)

Seiko caliber 7B72 is a radio-controlled quartz movement that runs on a rechargeable battery (aka capacitor) connected to a solar sensor under the dial which collects and stores energy from light. Timepieces with this movement were introduced in late 2019 for the Japan domestic market (JDM).

Radio-Controlled Timekeeping:

The radio-controlled features means that watches with this calibre are able to connect to radio towers (Cesium Atomic Clock) in order to receive data about the current time. The watch then uses that information to automatically set the time accordingly.

In Seiko’s own words:

“This watch sets the time and date by automatically receiving a radio signal at a fixed time. It automatically receives a radio signal before 2:00 AM, 3:00 AM and 4:00 AM.” -Seiko 7B72 user manual, page 17

Similar Calibers:

There is a similar Seiko caliber 7B62. The 7B72 and 7B62 share the same manual, however, it is unclear what the differences are. If you know more about this, please discuss it in the comments below…

Additional Resources:

• Official 7B72 instructions manual (pdf)