The Seiko 6139 automatic chronograph – a historical movement in its own right, like the full-serviced 1975 Seiko 6139-6012 "Bruce Lee" chronograph here, on its original stainless-steel "railroad" bracelet – was one of the first automatic chronographs created and ranks with Zenith’s El Primero and Heuer’s Calibre 11. 
 
Back in the late 1960's, Heuer and Zenith had taken hold of the entire sports watch industry by racing to become the first to produce an automatic chronograph.  It has been debated who won, but in the background of this skirmish, Seiko quietly created their own at the same time, beating the Swiss at their own game – the Seiko Ref. 6139 calibre.
 
Of note, this Seiko 6139 variant received its nickname by regularly being worn by Bruce Lee - yes, that Bruce Lee.  From the 2021 GQ article, "Why I Bought Bruce Lee's Watch," - "Be Water," ESPN’s moving documentary about Bruce Lee, artfully reframes the martial arts icon as a protest figure who spent his entire life fighting for equality and respect both onscreen and off."
 
"It’s also got a lot of footage of Bruce Lee wearing dope stuff.  The first time I watched it last June, I caught a glimpse of something intriguing in an archival photo of Bruce in a production meeting.  There, on his wrist, was a mysterious shiny band with a series of holes along the side.  Was it a bracelet?  A watch band?  A few minutes of Googling delivered an answer: it was a Seiko 6139 automatic chronograph, Bruce’s watch of choice in the final years of his life."
 
"Just like that, I had a dream watch.  I’d already been considering a Seiko as it was, for their value, reliability, and understated good looks.  But a Seiko cosigned by Bruce Lee?  That’s a whole other level of covetable..."
 
During the early months of 1969, Seiko put the final touches on its revolutionary 6139 chronograph - in fact, the Japanese company first began putting the 6139 in automatic chronographs as early as January of the same year.
 
Seiko published its first advertisement for their new automatic 6139 chronograph in February 1969, easily beating the Swiss - however, the company was concentrating on the release of the world's first quartz watch, the Astron, which would completely disrupt the watch world as it was known at the time (again, much to the chagrin of the Swiss watch industry, we're certain). We possess 6139 dials dating back to October 1968, indicating Seiko beat all other rivals to produce the world's first automatic chronograph.  Period.

With this movement, Seiko set the standard, which was followed by the Swiss watch industries 20 years later.  The same movement configuration was adopted by Rolex when it made its own in-house movement for the Daytona in 2000, 30 years after Seiko released the caliber 6139 and 6138.

This Seiko 6139 is on its original stainless-steel bracelet, and with nylon strap, springbar tool, and rugged travel case.