Seiko Marinemaster 300M Green SBDX021 - SLA019

The Seiko Prospex Marinemaster 300M Green SBDX021, known internationally as the SLA019, is one of the most collectible modern Seiko professional divers and was created in 2018 to celebrate the 50th anniversary of Seiko’s groundbreaking 1968 300-meter Hi-Beat diver. Nicknamed the “Deep Forest,” this special edition features a rich green dial and matching zirconia ceramic unidirectional bezel inspired by the ancient cedar forests of Yakushima, Japan’s first UNESCO Natural World Heritage site and a renowned diving destination. The substantial 44.3mm stainless steel case receives Seiko’s super-hard coating and is paired with a sapphire crystal, professional-grade LumiBrite, screw-down crown, and 300 meters of saturation-diving water resistance. Most importantly for collectors, the SBDX021/SLA019 was produced as a limited edition of only 1,968 individually numbered pieces worldwide, directly referencing the year of Seiko’s historic professional diver.

Powering the SBDX021 is Seiko’s premium Caliber 8L35, a 26-jewel automatic movement hand-assembled and adjusted by Seiko’s master watchmakers at the Shizukuishi Watch Studio. Operating at 28,800 vibrations per hour and providing approximately 50 hours of power reserve, the 8L35 offers hacking seconds, manual winding, and the robust construction required for a professional saturation diver. The SLA019 was also an important transitional model for the Marinemaster lineage, upgrading the formula with a sapphire crystal and highly scratch-resistant ceramic bezel while retaining the imposing case architecture and serious diving capability enthusiasts associate with the legendary MM300. Delivered on a stainless steel bracelet with an additional accordion-style silicone dive strap, the limited-production SBDX021 “Deep Forest” combines exceptional Japanese craftsmanship, genuine professional specifications, and a historically significant anniversary connection, making it one of the standout Seiko divers of the modern era.

Reference: SBDX021 and/or SLA019

Limited: 000X/1968

Dated: Undated

Bezel Aligns

Dial: Green

Bracelet: Stainless Steel Bracelet and Unworn Black Rubber Strap

Case: 44.3mm x 15.4mm Thickness - Stainless Steel

Lug Width: 20mm

Movement: 8L35 - Automatic

Functions: Hours, Minutes, Second, Date

Box and Papers: Box and Papers (Inner box falling apart)

Crystal: Hardlex

Bracelet size: 7.75”

Case has little to no wear. Bracelet has little to no wear. Strap is unworn. Dial, hands, and crystal have no wear. Watch is running within spec.

Seiko's history began in 1881 when Kintaro Hattori opened a watch shop in Tokyo. In 1892, he established Seikosha, a factory for producing wall clocks. The company quickly progressed, creating Japan's first wristwatch, the Laurel, in 1913. Despite setbacks like the Great Kanto Earthquake of 1923, Seiko persevered, launching its first watch under the Seiko brand name in 1924.

The post-World War II era saw Seiko's rapid growth and innovation. They introduced Japan's first automatic wristwatch in 1956 and launched the prestigious Grand Seiko line in 1960. Seiko achieved international recognition for accuracy in 1968, winning a Geneva Observatory competition. 

The company made a name for its divers in 1965 with the introduction of their first professional dive watch, the 62MAS. This was followed by the iconic 6159-7001 in 1968, which was water-resistant to 300 meters. Seiko gained international recognition in 1975 with the release of the 6159-7010, nicknamed the "Tuna Can" due to its distinctive case shape. In 1969, they revolutionized the industry with the Astron, the world's first quartz wristwatch, ushering a new era of watchmaking that would send waves across the industry through the 70s and 80s. From its humble beginnings to becoming a global watchmaking giant, Seiko's history is characterized by resilience, technological advancement, and a commitment to precision.