Let's get this out of the way - there's only two watch companies with such strong reputations for making tool watches that can make patina - evidence of a life lived with the purpose that a tool watch was designed for - attractive. Namely, a Swiss company that starts with an "R" and...Seiko.
There exist numerous vintage Seiko divers popular with "Seikoholics" collectors, but few more so than the venerable 6306 series - like this 1979 Seiko 6306-7001 automatic diver here, on its original rubber Seiko GL831 dive strap.
Between 1965 and 1975, Seiko brilliantly conceived, designed, and produced three generations of classic ISO-certified 150 m divers’ watches, in chronological order - the 62MAS, 6105-8000/9, and the 6105-8010/9.
Then 1976 arrived...
That year, Seiko debuted its replacement for its 6105, conceived in two different specifications - one for the domestic Japanese Domestic Market and the other for overseas.
The latter international variant - the 6309 - featured a 17 jewel 6309A automatic movement, fitted with bilingual day wheels appropriate for the target geographic it would be sold in, while the former Japan domestic version - the 6306 - was to be fitted with a more advanced 21 jewel 6306A movement, with seconds hack capability and an English/Kanji Japanese day wheel.
The 6306 lived a rather short life in between the 6105 and 6309, and was produced from 1976 to 1981, when Seiko would favor the 6309 until it too was replaced with the 7002 diver in 1988. The 6306 and 6309’s were a successful effort by Seiko to improve the 6105 movement, which allowed for greater lifespan, robustness, and ease of maintenance.
Both were popular with the U.S. military, akin to the Seiko model it replaced, the 6105 - its (much more expensive) forefather - and quickly became the staple of the working diver.
In fact, the 6306 & 6309 divers gained - and still hold - respect worldwide, to include from individuals from literally all walks of life. Military, police, firefighters, divers and regular people all over rave over the combination of ergonomics, aesthetics, reliability, legibility, affordability, durability and strength. All of which have shown to form a legendary combination.
This Seiko 6306 JDM diver comes on its original rubber Seiko GL831 dive strap, and with nylon strap, rugged travel case, and springbar tool.
1979 Seiko 6306-7001 JDM Automatic Diver, w/Original Strap
DIAL: Black Suwa-signed dial, with reddish-yellow "water resist" lettering, unusual given this lettering is usually UV-faded to a light yellow. English/Kanji Japanese language variants on the day wheel. Like the dial, the handset evinces no lume patina; dial and handset lume shines following exposure to bright light - lume also matches throughout dial and handset.
BEZEL: Bi-directional and ratchets with a click; bezel insert features little substantial wear - these are usually first to be damaged when these diver's were used as designed, ie: hard.
CASE: Stainless-steel cushion case measures in at a hefty 44mm (w/o crown, 44.5mm with) x 45mm, with brushed finish remaining on case top and sharp case lines. Matching caseback, with its frosted Seiko "wave" emblem crisp and defined - of note, remnants of the original Seiko case back sticker is present around/within the iconic Seiko tsunami wave.
CRYSTAL: Seiko 6306 Hardlex crystal, no scratches or cracks.
BAND: This 6306 comes on its original rubber Seiko GL831 strap, which remains pliant and without cracks; it also comes with a black nylon strap.
MOVEMENT: Seiko 6300-series automatic movement, 21 jewels, manufactured in April 1979; movement hacks, as designed
CROWN: Screw-down unsigned stainless-steel crown operates as designed.