Seiko serial number 928558 (February 1969 production 8558)
This watch was produced in 1969. It was one of the first models Seiko produced with their new 6139 chronograph movement. The second sweep and minute totalizer hand on this watch are incorrect, the dial bezels for the day/date apertures are incorrect and the internal bezel ring doesn’t appear original. The watch case is correctly notched by the crown and the movement is the 6139A 21 jewel version found in these watches till early 1970. The 6139A movement, notched case and Speed Timer and Sports 5 labeling of this watch are the hallmarks of earliest Asian market versions.
Unlike Zenith and Heuer, the only proof of Seiko’s creation of an automatic chronograph in 1969 was their production, since Seiko never held a press conference or announced their achievement. Based on decoding of serial numbers of watches in the hands of collectors (1st digit of Seiko serial numbers indicate year of production, 2nd digit indicates month of production), it appears Seiko was in full serial production of 6139s in February of 1969. Based on the serial number of this watch, it would appear they produced over 8000 watches in February.
Seiko began retail sales of 6139 chronographs in the Japan in May of 1969.