Seiko 6309-7040 Diver

Seiko 6309-7040 Diver

Seiko released its first dive watch in 1965, the Reference 6217, which was water-resistant to 150 meters and had a rotating bezel, luminous hour markers.

It was competitively-priced compared to Swiss divers, but for Seiko, it was only the beginning.

Seiko followed up the 6217 with the Reference 6105. Introduced in 1968, the 6105 was powered by the Calibre 6105, a 17 jewel movement that came in two variations, the 6105A and the 6105B. Seiko also produced the 6105 with two case types: one, a chunky, asymmetrical cushion case, and a svelte, symmetrical cushion case. 

It was the 6105 that American GIs favored during the Vietnam War, due to its ready availability at PXes throughout the peninsula. 

In 1976, Seiko followed up the 6105 with the 6309. Like its predecessor, the 6309 used a cushion case, but departed from the 6105's asymmetrical case design, instead utilizing a hefty 42mm symmetrical cushion or "turtle" case. The 6309 also added a day function to the 6105's simple date window; a revamped dial with circular luminous plots instead of rectangular ones; unique bell-shaped markers at 6 and 9 o'clock and a double bell at 12; and a thicker bi-directional bezel with two rings of knurling versus one, making it easier to operate with gloves. 

Produced for well over a decade, the 6309 has all the hallmarks of a proper tool watch. So strong was the 6309's DNA that Seiko recently reissued the design as the Prospex SRP-77X series. While a remake is all well and good, there's nothing quite like the real thing.

Despite its tough exterior, the 6309 has not quite reached the popularity or rarity of its older brother and has remained a solid bang-for-the-buck Seiko diver. Genuine, all-original examples are hard to track down thanks to an active aftermarket and many unscrupulous sellers, making finding one in the wild a real treat. 

This particular example dates from July 1978 and retains its thick, fat bevels on the lugs. Though it's seen years of use, it's remained intact, ready for another thirty years of wear.


Stainless steel cushion case is approximately 42mm (excluding crown). Seiko Reference 6309. Seiko Caliber 6309 Automatic Movement. Circa July 1978.

Overall Condition: Stainless steel cushion case is in very good condition with minimal signs of use and wear and no signs of overpolishing. Rotating bezel has some dings and scratches throughout but is in otherwise very good condition. Dial is in very good condition with patina to the luminescent elements of the hour markers and hands. Unsigned crown. Seiko case back has some signs of wear and use but is in otherwise very good condition.

Includes one 20mm textured cloth strap and two 20mm nylon straps from Crown & Buckle

SKU: TT01148

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