Seiko's Turtle Series: From the 6306 to Modern King Turtle Marvels

The Humble Beginnings: The Iconic 6306

When you think of legendary watches that have carved their niche in horology, few collections elicit the same respect and admiration as Seiko's Turtle series. The genesis of this iconic series was the 6306, launched in the mid-1970s—a period that was bustling with innovations in the dive watch landscape. Yet even in such a competitive market, the 6306 was a veritable revelation. It didn't merely meet the standards; it reset them.

The Iconic Seiko 6306

Powered by the automatic Calibre 6306A movement, this magnificent watch operated at a robust 21,600 BPH (Beats Per Hour). This kind of performance was unprecedented for a dive watch in its price range, effectively setting new benchmarks for what a functional yet fashionable dive watch could, and should, be.

From its debut, the 6306 quickly found its home on the wrists of dedicated divers and adventure enthusiasts. Its rugged design, dependable performance, and water-resistant features (150m) rendered it an instant classic in the underwater realm. Such was its impact that the watch didn't just stay confined to professional divers. It transitioned seamlessly from the ocean depths to the urban jungle, becoming a staple for the adventurous, stylish, vibrant, and confident individual—pretty much everything that the modern Seiko Turtle series encapsulates.

The unidirectional, aluminium bezel provided not just aesthetic appeal but functional utility. It allowed divers to easily keep track of their time underwater, reducing any room for error—a crucial feature when you're tens of meters below sea level.

And it wasn't just the functional aspects that won hearts; the 6306, with its distinct cushion-shaped case, appealed to the aesthetic sensibilities of watch aficionados. The Hardlex crystal provided a clear yet durable window into the dial, proving that you didn't need to compromise on form for function.

6306 Movement

The 6306 model was truly a game-changer, laying the groundwork for a series of successors, each fine-tuned with advancements that honoured the watch's original spirit while ushering it into modernity. Honourable mentions to the a variant famously known as SCUBAPRO 450. Developed in collaboration with the diving gear brand Scubapro and the Turtle didn't just stop at conquering the seas; it ventured into military service with the 6306 MSST - Japan’s Marine Self-Defense Force.

The 6309 Model

Following the 6306, the 6309 model continued to feature the Calibre 6309A movement, an automatic, non-hand-winding movement operating at 21,600 BPH, much like its predecessor. However, its production run until 1988 saw several variations in the dial and case, thus providing collectors with options to satiate their specific tastes. Like the 6306, it sported a Hardlex crystal and an aluminium unidirectional bezel.

The Iconic Seiko 6309 Scuba Pro

The SRP77x Models

Fast forward to the modern era, the SRP77x series—or 'New Turtle' as they're often called—made a splash in the dive watch community in 2016. These models came equipped with the upgraded Calibre 4R36 movement, which not only offered automatic winding but also allowed for hand-winding—a significant development over previous models.


The movement remained consistent at 21,600 BPH, but the power reserve saw an improvement, as well as the addition of a day-date complication & rating up to 200m. The SRP77x retained the Hardlex crystal and aluminium bezel, keeping the series true to its roots while infusing it with modern functionalities. Spin off series like the SRPC23 also retained all the "new turtle" spec but offered alternative styles such as the Anthracite dial. (pictured below)


The Mini Turtle

The Mini Turtle (2018) diverged slightly but importantly from its bigger siblings by incorporating the Calibre 4R35 movement. With a slimmer profile, the Mini Turtle catered to those who sought the Turtle's robustness in a more compact size. The 4R35 movement offers hand-winding capabilities and features a slightly lower power reserve than the 4R36, making it a fantastic entry-point for new collectors while still enticing the seasoned ones. Popular models such as the SRPC35, SRPC41 & the colourful Zimbes SRPD17/19 are very collectable.

SRPD19 zimbe mini turtle

The King Turtle

As the pinnacle of the Turtle series, the King Turtle comes outfitted with deluxe features like a sapphire crystal and a ceramic bezel, making it a cut above the rest in terms of luxury. These models come with the 4R36 movement, echoing the SRP77x series but enveloping it in a sheen of modern sophistication. The King Turtle thus offers a blend of rugged functionality and refined aesthetics that's hard to find in other dive watches in the same price range. The SRPE05 with its "grenade" style green dial has become very popular and represents exceptional value for money.

seiko king turtle

Whether you are a seasoned collector fascinated by the evolution of the Turtle series or a newbie enticed by its rich history, diver styling and current offerings, the story of the 6306 offers something for everyone. Its legacy serves as a testament to Seiko's commitment to innovation, quality, and timeless style—a legacy that continues to expand and evolve with each new model.

There is also a difference with the edge of the bezel between the Turtle & King Turtle as shown in the picture below. Turtle on the left, King Turtle on the right.
two seiko turtles

So, if you’re looking to strap on a piece of horological history with unmatched style and functionality, why not consider one of our FKM Watch Straps? Whether you own a classic 6306 or have your eyes on a King Turtle, these replacement watch straps offer the durability, water resistance, and UV protection to complement your Seiko Turtle perfectly. After all, every legendary watch deserves an equally exceptional strap. Adventure awaits, wear it well.

The Seiko Turtle isn’t just a watch; it’s a statement. A statement of resilience, functionality, and unconventional beauty. Whether you're a seasoned horologist or a casual watch enthusiast, strapping on a Turtle is like joining an exclusive club—one that understands and appreciates the finer subtleties of watchmaking. If your are looking to join the "club" check out these models.

  • 6306-7000 If you can find one in all original condition they may well be over AU$3,000
  • SRP777 Popular new Generation Turtle model.
    Turtle 777
  • SRPC23 New Generation but with the anthracite dial, very nice.
    Turtle Gray Sunburst
  • SRPA21 New Generation PADI Variant, great colour-way.
    SRPA21 Turtle Padi
  • SRPC95 Nemo version, again a great colour-way.
    Turtle Nemo
  • SRPF77 King Turtle Manta Ray, terrific dial.
    King Turtle Manta Ray
  • SRPE05 King Turtle variant with the green grenade dial. Future classic.
    King Turtle Green Waffle
  • SRPJ53K King Turtle variant with the green grenade dial. Special Australian Variant.
    Seiko Prospex 'Eucalyptus' Australian Limited Edition SRPJ53K
  • SRPC41 Mini Turtle variant, PADI Dial, hard to find.
    Mini Turtle PADI
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