Seiko Caliber 7548A

Manufacturer	Seiko Time Corp.
Caliber Number	7548, 7548A
Movement Type	Quartz, battery-powered
Display	Analog
Diameter	27mm
Height	4.6mm
Jewel Count	5 jewels
Frequency	32,768 Hz
Accuracy Rating	Less than 15 seconds/month (less than 3 minutes/year)
Battery Cell #	SR43SW (aka 386/301) / silver oxide / 1.55 V
Battery Life	~3 years
Driving System	2 pole step motor
Regulator?	Trimmer condenser
Hand Count	3
Functions	Central hours; central minutes; central seconds; day of the week at 3:00; date at 3:00
Hacking Seconds?	Yes
Quickset Date?	Yes
Other Features	Bilingual day, AC reset, low battery indicator (EOL)
Plastic Parts?	Yes
Country of Manufacture	Made in Japan
Known Models	Seiko Series 75 Diver 150m, PYH011, PYH018 (Add your watch to the comments below…)

The Seiko caliber 7548A is a vintage quartz movement from the 1980s (originally introduced in 1979?).

Note: This calibre is sometimes misspelled as 7S48 or 7S48A.

Cal. 7548 VS 7546:

There is a similar caliber 7546A sharing most of the same specs (dimensions, accuracy, etc.) with a few notable differences:

	7548A	7546A
Jewels	5	4
Battery Life	3 years	5 years

The 7548 is also said to have a higher torque rating than the 7546.

Note: Some components (particularly calendar parts) are also interchangeable with the caliber 63 series.

Video – Seiko 7548-700B Disassembly:

Video – Seiko 7548-700B Assembly:

Video – Why you don’t want to leave an old battery in your watch:

Additional Resources:

• Official 7548 tech sheets (pdf)