Seiko's Ref. 6139 automatic chronograph – a historical movement in its own right, like this quite rare 1972 Seiko 6139-6002 "Teal Sunrise" here, on its original SpeedTimer bracelet – was one of the first automatic chronographs created and ranks with Zenith’s El Primero and Heuer’s Calibre 11. 
 
Seiko's 1972 Teal Sunrise 6139 chronograph is easily the most rare of the couple dozen or so variants of the Japanese watch company's famed 6139, and is frequently "feiko'd" - in fact, at any given time the dozen or so you can find on a certain popular online auction site are all feiko.  Every single one of them - feiko dial, hands, bezel, and even bracelets.  
 
The easiest tell?  The Teal Sunrise is exceedingly rare due to Seiko producing it for a scant two months, in November and December 1972.  If the first two digits of the case back serial number do not read "2N" or "2D", its feiko.   
 
Back in the 1970’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 awidely debated who won, but in the background of the skirmish Seiko quietly created their own, beating the Swiss at their own game – the Seiko Ref. 6139 automatic chronograph.
 
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 Japanese company was concentrating instead on the release of the world's first quartz watch, the Astron, which would radically 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 to be one of the hallmarks of a superior automatic chronograph movement.  The 6139 features an automatic column wheel timing control and an integrated chronograph, which means the entire movement was designed and built to be a chronograph, vice being an automatic movement with a mere timing module.  The movement features a single register chronograph allowing time to be measured in increments of 30 minutes.
 
This Seiko 6139 Teal Sunrise comes on its difficult to find original stainless-steel SpeedTimer bracelet, and with its inner/outer boxes, SpeedTimer 6139 instructions manual, nylon strap, rugged travel case, and springbar tool.