Up for sale is a vintage Seiko 6138-8039 chronograph watch. This is the model that is unofficially nicknamed the "John Player Special" by collectors, because the black/gold color combo matches the livery of 1970s Lotus Formula 1 cars that were sponsored by John Player & Company Tobacco. The serial number dates this example to August of 1976.
The Seiko 6138 line of chronographs was Seiko's second major type of automatic chrono, after the 6139. The main difference is that the 6138 is a "dual register" chrono, measuring seconds, minutes, and hours, as opposed to just seconds and minutes with the 6139. The 6138 also had one major improvement - it can hand-wind at the crown, as opposed to the 6139, which can only wind through motion. Both movements are "column wheel" with a "vertical clutch" - I have very little understanding of what that means except that they are complicated, expensive to produce, and can generally only be found in high-end modern chronographs.
Mechanically, this example is running well, though I have no idea when (if ever) it was last serviced. The hands set via the crown as they should, and the day/date works properly both via the passage of the hands at midnight and via the quick-set through the crown when it is pulled out to the middle setting position. The chronograph buttons also work properly (no "sticking"), and the chrono hands start, stop, and reset to 0 all as they should. The watch also hand-winds as it should. I wound it up, started the chrono, and checked the timekeeping 19 hours later and it had gained 14 seconds. That's not terrible, but it could probably be improved with regulation.
Cosmetically, the watch is in nice shape overall, but not perfect. The case shows its original contrasting brushed/polished finish showing very well and has sharp case lines. Obviously, please check the photos out yourself. The watch has its original bracelet, and it is quite long and probably full size - it is pictured worn comfortably on my huge 7.75" wrist.