There exist many legendary vintage Seiko automatic references, but few more so than the venerable Seiko 6309 series - like the 1978 Seiko 6309-8120 automatic watch here, on its original Seiko-signed stainless-steel bracelet.
Crowned by Watches of Espionage (WoE) as "One of history’s most important diving & military watches," the 6309 - albeit not the exact model here, but the 6309-7040/9 model - was popular with the U.S. military (and militaries further afield from the America, as well), akin to the Seiko model it replaced, the 6105 - its much more expensive forefather.
After it's debut, the Seiko 6309 quickly became the staple of the USMIL (both regular forces and Special Forces) and commercial divers everywhere. U.S. Navy Naval Special Warfare units - aka Navy SEALs - favored Seiko divers, in particular the 6309.
The 6309 series of watches was the third generation of Seiko’s recreational and professional divers. The 6309 line replaced the 6105 in 1976 and was produced until 1988, when Seiko replaced it with the 7002 diver.
Produced more or less concurrently was the 6306, which lived a short life in between the 6105 and down-jeweled and less complex 6309, from 1976 to 1981, when Seiko would favor the 6309 until it too was replaced with the 7002 diver in 1988. The 6306 calibre was a successful effort by Seiko to improve the 6105 movement, which allowed for greater lifespan, robustness, and ease of maintenance.
In turn, the Seiko 6309 - like this one here - was also a successful effort by the Japanese watch manufacturer to improve the 6105 movement, which allowed for greater lifespan, robustness, and ease of maintenance, while also reducing the complexity of the interim 6306 movement.
Oh - and did we mention both Rolling Stones legendary frontman Mic Jagger and actors Ed Harris (who also wore a Seiko 6139 "Cevert" in the "Apollo 13" film, but that's another story) and John Candy personally owned one? Harris' appears to be his own 6309, as he has worn it in multiple films throughout the last three decades. A slew of other actors have worn the same watch throughout the past several decades on various television shows, Erik Estrada in "CHiPS" (1977-1983) and Nicholas Gonzalez in "Blue Ridge" (2024)
Moves like Jagger, indeed...
This Seiko 6309 automatic comes on it's original stainless-steel Seiko bracelet, and with nylon strap, rugged travel case, and springbar tool.
1978 Seiko 6309-8120 Automatic Dive Watch
DIAL: Unmarred lightly-textured silver Suwa-signed Seiko dial, with crisp dial lettering1. Date and day functions - with Roman numeral/English day variants - at the 3 o'clock position functions as designed. Dial lume and handset lume continues to shine following exposure to bright light.
CASE: Stainless-steel case measures 37.5mm (w/o crown, 38mm with) x 42mm, with sharp case lines. Matching caseback, with crisp engravings.
CRYSTAL: Hardlex crystal, no scratches, blemishes, or imperfections.
BAND: This Seiko 6309 comes on its original Seiko-signed stainless-steel bracelet, which will fit up to an approx. eight inch wrist; it also comes with a dark blue, green, and white nylon strap.
MOVEMENT: 6300-series Seiko automatic movement, 17 jewels and manufactured in July 1978.
Find a great Watches of Espionage video on the love of militaries worldwide for Seiko on YouTube, here!