SEIKO Scuba Pro 450 6306-7001 44mm Circa 1970s

The SEIKO 6306-7001: Japan’s Domestic Diver with Professional Ambition

In the late 1970s, Seiko’s reputation as a serious tool watch manufacturer was already well established. The 6105 and early 6309 models had set benchmarks for reliability in adverse conditions, worn everywhere from the jungles of Vietnam to deep-sea diving expeditions. But there was one diver that quietly raised the bar—though only available in Japan. The Seiko 6306-7001, produced from 1976 to 1981, was the domestic market’s professional upgrade to the globally available 6309. It didn’t shout for attention. It didn’t need to. Beneath the surface, it was better equipped, more refined, and ultimately rarer. This is the story of Seiko’s JDM diver that’s now firmly in the crosshairs of serious vintage collectors.

Origins and Collaboration

In the 1970s, Seiko collaborated with Scubapro, a renowned diving equipment manufacturer, to produce a limited-edition dive watch tailored for professional divers. This partnership led to the creation of the Seiko 6306-7001 Scubapro 450, a model that combined Seiko’s watchmaking expertise with Scubapro’s diving insights.

The Scubapro 450 was based on Seiko’s 6306-7001 model, which was itself an evolution of the 6309 series. The 6306 featured enhancements such as a hacking mechanism, allowing the seconds hand to be stopped for precise time setting, and a Kanji day wheel, catering to the Japanese domestic market. The collaboration with Scubapro added a unique branding element to the watch, making it distinct from other models in the 6306 series.

Design and Features

The Seiko 6306-7001 Scubapro 450 boasts a robust 44mm stainless steel case with a cushion-shaped design, earning it the nickname “Turtle” among enthusiasts. Its unidirectional rotating bezel, essential for tracking dive times, is paired with a Hardlex crystal—a proprietary hardened mineral glass developed by Seiko for enhanced durability and scratch resistance.

The matte black dial features large, luminescent hour markers and hands for optimal readability underwater. The day-date display at 3 o’clock includes both English and Kanji characters, reflecting its Japanese domestic market roots. The Scubapro 450 branding is prominently displayed above the 6 o’clock position, distinguishing it from standard models.

At its core, the watch houses the 6306A automatic movement, a 21-jewel caliber operating at 21,600 beats per hour. This movement is notable for its hacking feature and increased jewel count compared to its international counterpart, the 6309, which lacked hacking and had 17 jewels.

Production and Rarity

The Seiko 6306-7001 Scubapro 450 was produced between 1978 and 1979, with estimates suggesting that only around 1,000 units were made. This limited production run, combined with its unique branding and features, has contributed to its desirability among collectors.

Interestingly, while the majority of these watches were produced within this two-year span, some examples have surfaced with caseback dates from 1976, 1977, and even 1983. This has led to discussions among collectors about the authenticity and production timelines of certain pieces. It’s essential for potential buyers to be aware of these anomalies and consult with experts when verifying a watch’s authenticity.

A Diver’s Watch in a Diver’s Country

To understand the 6306-7001, you have to understand its environment. Japan is a country deeply connected to the ocean—from traditional Ama divers to its massive maritime industry. It’s also a place where Seiko built some of the most revered diving watches ever made, including the 62MAS and the high-end 6159-7010 “Grandfather Tuna.” Within this legacy, the 6306-7001 occupied a practical, mid-tier position: not the brand’s most extreme offering, but a clear step up from its mass-market peers.

It was intended solely for the Japanese market, which already had a strong appetite for mechanical innovation and practical refinement. This watch needed to appeal to professional and serious recreational divers—people who valued precision, reliability, and build quality above all else. It wasn’t a fashion statement. It was a tool, and Seiko engineered it accordingly.

Case and Construction

The Seiko 6306-7001 shares its case with the globally sold 6309-7040/7049, but there are key distinctions. The case is large by vintage standards—measuring 44mm wide, 48mm lug-to-lug, and approximately 13mm thick. The cushion-shaped design offers excellent wrist stability, especially important underwater. The screw-down crown is located at 4 o’clock, recessed slightly to avoid wrist interference, a design choice rooted in the earlier 6105 series.

Water resistance was rated at 150 metres. Though modest by today’s standards, it was more than enough for skin and recreational SCUBA diving of the era. A screw-down caseback with the signature tsunami wave emblem added both style and security. The bi-directional bezel, typical of the time, featured a 60-minute scale with clickless rotation—easy to adjust with gloves or underwater. It wasn’t ISO-certified, but it was built for real-world use, and many examples survive today in fully functional condition.

Dial and Hands

Functionality dominates the dial design. Matte black with large, luminous indices, the 6306-7001 ensured maximum legibility in low light and murky water. Printed lume plots are surrounded by white minute and hour markers, offering strong contrast. The hands follow the same principle: oversized, filled with lume, and distinctive in shape. The minute hand, especially, stands out with its large arrow tip—essential for tracking elapsed dive time.

The second hand features a lollipop tip with lume, an important detail for divers: the constant movement of a lumed seconds hand reassures the wearer that the watch is running during a dive.

One subtle but important difference is the text layout. The dial reads “Automatic” above “150m,” with “JAPAN 6306” printed at 6 o’clock. Some examples include the Suwa factory logo, which helps enthusiasts trace manufacturing origin and batch details.

The Movement: Calibre 6306A

Here lies the biggest upgrade over the 6309: the Seiko 6306 movement. A 21-jewel, hacking automatic movement, the 6306A beats at 21,600 vph and offers a power reserve of around 47 hours. While the 6309 used a non-hacking calibre (meaning you couldn’t stop the second hand when pulling out the crown), the 6306 featured hacking seconds—a crucial feature for accurate time-setting, especially in professional contexts.

The movement was robust, easy to service, and built to last decades with proper care. Its jewel count was increased from 17 to 21 over the 6309, primarily to improve long-term durability and reduce friction in key components. It also featured quickset for the day and date. Most notably for collectors, the 6306-7001 included Kanji-English day wheels—something only found on Japanese Domestic Market (JDM) models, and a distinctive, appreciated feature today.

Japan Domestic Market Exclusivity

The 6306-7001 was never sold outside Japan, which makes it considerably rarer than the export 6309 series. Seiko didn’t market the watch aggressively overseas, possibly because it overlapped too closely with the 6309-7040/7049. The upgrades—hacking movement, higher jewel count, Kanji day wheel—were considered refinements rather than dramatic shifts. But for purists and professionals in Japan, these small changes mattered.

Today, that exclusivity gives the 6306-7001 an undeniable allure. With fewer examples produced and even fewer surviving in original condition, they now command a premium over comparable 6309 models. JDM collectors know what they’re looking at—and what they’re looking for.

Model Evolution and Short Production Run

Seiko began producing the 6306-7001 in 1976. It ran until 1981, replaced eventually by quartz divers and then later by the 7C43 and 7S26-based SKX series. Within that five-year production span, there were two main versions of the 6306.

• 6306-7000: The earliest iteration, produced briefly in 1976. It featured slightly different dial text and no Suwa logo.
  
• 6306-7001: The more common version (though still rare), with a Suwa dial logo and subtle refinements to dial layout and caseback engraving.

Both share the same core components and movement, but collectors tend to seek out the 7001 for its more refined execution and better parts availability.

Wearing the 6306-7001 Today

Despite its age, the 6306-7001 wears beautifully on the wrist. Its cushion case hugs the arm, the 44mm width offset by short lugs. It works on the original rubber strap (if you can find one) or on period-correct Seiko ZLM01 rubber, Tropic-style straps, or a waffle strap for extra vintage charm.

It’s equally at home on a NATO or even a bead-of-rice bracelet, giving it an understated vintage diver look. With water resistance long gone in most vintage examples, this is a watch best kept dry unless fully pressure-tested and resealed by a competent watchmaker.

Still, the appeal of the 6306-7001 isn’t just skin-deep. It’s the kind of watch that rewards close inspection—where the differences between it and a standard 6309 aren’t just cosmetic but practical. The hacking movement, Kanji date wheel, and limited JDM release all signal that this was made for someone who needed more from their watch.

Final Thoughts

The Seiko 6306-7001 is a watch that whispers, not shouts. It doesn’t have the pop culture fame of the 6105 “Captain Willard” or the international ubiquity of the SKX007. But for those who know, it represents a sweet spot in Seiko’s diving lineage—where durability met refinement, and domestic exclusivity gave it a quieter prestige.

It was a professional tool, made for a professional audience, in a country that appreciated precision. In today’s market of hyped reissues and homage pieces, the original 6306-7001 remains a gem—genuine, useful, and still under the radar.

It may have been designed for Japan, but its legacy now extends far beyond its shores.

• Case and bracelet in good vintage condition.
• Light hairline scratches are visible around the case indicating the watch has been worn for its intended purposes. 
• The rubber strap is in good condition. 
• The seiko hardlex crystal has light scratches.

• Dial is in great condition, with a creamy patina forming.
• Hands lightly oxidised but remain in great condition.