Seiko 6138-3009, February 1972.
21j automatic chronograph
Hand-winding, and automatic winding
42mm x 48mm x 16mm, w/ 18mm lugs
All stainless steel
double-register design with 30-minute and 12-hr counters
Spanish / English daywheel
Hardlex mineral crystal, two-part contstruction
Originally water resistant to 70 meters