Seiko's 6139 automatic chronograph - a historical movement in its own right, like this 1970 Seiko 6139-6011 "Deep Blue" proof/proof chronograph here - was one of the first automatic chronograph movements created, and rightly counts itself within the ranks of the world's first automatic chronographs, with Heuer's Calibre 11 and Zenith/Movado’s El Primero movements.
 
Seiko did their homework when they designed these deep blue dials, and pictures do not do these justice - these dials are amazing to behold in person, and this dial here is no different.
 
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 widely 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. 
 
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.
 
The 6139 was the first chronograph to have a vertical clutch, a feature considered by many to be one of the hallmarks of a superior automatic chronograph movement.  The 6139 also features an automatic column wheel timing control, vertical coupling mechanism, and is an integrated chronograph – the first in the world – which means the entire 6139 movement was designed and built to be a chronograph, vice being an automatic movement with a mere timing module added (**cough cough** the Calibre 11).
 
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 particular Seiko 6139, the 601x variant, represents yet another variant of Seiko's famed 6139 automatic chronograph line.
 
This 6139 comes on an Uncle Straps stainless-steel "railroad" bracelet, and with nylon strap, rugged travel case, and springbar tool.