The Seiko 6139 automatic chronograph – a historical movement in its own right, like this full-serviced 1970 Seiko 6139-7010 SpeedTimer "Military" automatic chronograph here – was one of the first automatic chronographs created and ranks with Zenith’s El Primero and Heuer’s Calibre 11.
 
The best thing about these made in Japan-only Seiko 6139-7010's?  They feature atypical Arabic numbers counting the hours - Seiko used this designed sparingly during this era, and it gives the watch a great military stance.
 
And it appeared the Japanese military, in the form of the Japanese Defense Forces, agreed - these were issued to the JDF navy (JMSDF) and air (JASDF) forces; issued examples are exceedingly rare, and feature military insignia on the case back and JDF in Kanji Japanese.  A 1981 Japanese TV special, "The Last Show," highlighted JASDF pilots and their U.S.-provided F-86 Sabre and Mitsubishi T-2 fighter jets.
 
The interviews revolved around the JASDF aerobatic flying squad (akin to the USAF Thunderbirds and Navy Blue Angels), the Blue Impulse, and their lengthy use of the F-86 Sabre before transitioning to Mitsubishi T-2's. 
 
And on the wrist of the JASDF pilots?  The Seiko 6139-701x, naturally.
 
Following the defeat of Japan in World War II, the JASDF was founded in 1954 with an initial 85 aircraft donated by the United States Air Force (USAF) – in modern times, it continues its use of USAF aircraft, to include the F-15 Eagle, F-35 Lightning, UH-60 Chinook, UH-60 Black Hawk, and a slew of other support airframes; it also flies domestically produced fighter jets, like the Mitsubishi F-2.

Founded officially in 1960 following a visit to Japan by the USAF Thunderbirds, the Blue Impulse was equipped initially with the F-86 Sabre, and would perform for the opening ceremony’s of the 1964 Summer Olympics in Tokyo, the first held in the Asia; it continues to perform for Olympics and other events to this day.

During the era the JASDF issued the Seiko 6139-701x to its pilots, the 1970s, its primary fighter jet airframe was the North American Aviation (now Boeing) F-86F Sabre, with nearly 500 acquired from the U.S. or assembled by Mitsubishi in Japan. 

The Sabre was best known as the USAF’s first swept wing fighter (and set the first official world speed record of 671 mph in late 1948), which could counter the similar Soviet MiG-15 in high-speed dogfights over the skies of the Korean War.
 
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 widely debated who won, but in the background of this skirmish, Seiko quietly created one theirs at the same time, beating the Swiss at their own game – the Seiko Ref. 6139.
 
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 November 1968, indicating Seiko beat all other rivals to produce the world's first automatic chronograph.  Period.
 
This Seiko 6139 "Military" comes on a leather-backed canvas strap, and with nylon strap, rugged travel case, and springbar tool.