Seiko Caliber 6138A

Manufacturer	Seiko
Caliber Number	6138A, 6138
Movement Type	Automatic, self-winding mechanical, chronograph
Diameter	27mm
Height	7.9mm
Jewel Count	21
Beat Rate / Frequency	21,600 bph / 3 Hz
Lift Angle	Unconfirmed
Power Reserve	Unconfirmed
Hand-Windable?	Yes
Anti-Shock Device	Diashock
Hand Count	5
Functions	Central hours; central minutes; central chronograph seconds; 12 hours chronograph counter at 12:00; 60 minutes chronograph counter at 6:00; day and date at 3:00
Hacking Seconds?	Unconfirmed
Country of Manufacture	Made in Japan
Known Models	Seiko Sports Speed-Timer (Add your watch to the comments below…)

The Seiko caliber 6138A is a vintage automatic column wheel chronograph movement. This chrono has a vertical bi-compax 12-6 layout, with a day/date at 3:00

Official Seiko documentation listed the 6138a as having the following features:

• An advanced automatic winding chronograph
• Easy-to-use, regular chronograph mechanism
• Seiko’s special clutch mechanism without starting/stopping errors
• Day and date instant setting device operated simply by revolving the crown
• Bilingual change-over mechanism for day indication selectable by preference
• Auxiliary hand winding device instantly usable for measuring time
• External devices with many functions

Additional Resources:

• More Seiko watch movements