The Seiko Prospex Marinemaster 1968 Heritage Diver SLA079J1 is a premium, professional-tier tool watch that reinterprets Seiko’s iconic high-beat dive watch from 1968. Considered a major evolution in the modern Marinemaster lineup, it offers significantly more wearable proportions and an upgraded, serviceable case design compared to the massive "MM300" models of the past.

• Case Profile: It features a 42.6mm case diameter and a slimmed-down 13.4mm thickness. Coupled with a 49.3mm lug-to-lug distance, it contours comfortably to the wrist while retaining its heavy-duty dive identity. 

• Dial & Bezel: A matte black dial with a grainy, sand-like texture provides contrast against oversized hour markers and sword-style hands. It features a matching, subtle date window between 4 and 5 o'clock. The unidirectional 120-click rotating bezel features an inky, deep black lacquered steel insert. 

• The Movement: Inside is the high-tier In-House Caliber 8L35 automatic movement. Hand-assembled at Seiko’s prestigious Shizukuishi Watch Studio alongside Grand Seiko movements, it beats at 28,800 vph, utilizes 26 jewels, and delivers a 50-hour power reserve. 

• Durability & Lume: Built out of stainless steel with a super-hard coating, it boasts a 300-meter (30 bar) water resistance rating. A double-domed sapphire crystal with an inner anti-reflective coating protects the dial. The hands, markers, and bezel pip are heavily coated in long-lasting LumiBrite.

• Feature	Specification	Source
  Reference	SLA079J1 / SLA079 (SBDX065 in Japan)
  Case Dimensions	42.6mm Width x 13.4mm Thickness x 49.3mm Lug-to-Lug
  Material	Stainless Steel with super-hard coating
  Water Resistance	300m / 1000ft (ISO Diver's)
  Movement	Seiko Caliber 8L35 (Automatic, Hacking, Hand-winding)
  Accuracy	+15 / -10 seconds per day
  Crystal	Dual-curved sapphire with inner anti-reflective coating
  Bracelet	Five-link steel, fold-over clasp with diver extension, 20mm lug width