In 1967 Seiko introduced their first ever professional diver's watch, the 6215-7000. It was designed for professional deep dive use and featured a one-piece case, and was capable of withstanding 300m of water pressure thanks to it's unique screw-down crystal gasket. One year later the 6215-7000 was replaced with this watch, the Marine Master 300 Reference 6159-7001. It features an improved hi-beat movement ticking 10 times per second! The Marine Master paved the way for many of the incredible dive watches that Seiko is known for today like the 62MAS, Turtle, & SKX.

Pre-owned Seiko MM300 Watch. Reference 6159-7001. Overall, this watch is in C, Fair condition.

- Ref No. : 6159-7001
- Serial No./Year: 922029-/-1969
- Case:
    44mm diameter, 19mm lug width, 14.2mm thickness, 50mm Lug-to-lug.
    Stainless Steel Monocoque 
- Crystal: Seiko Mineral Hardlex
- Movement & Accuracy: 
    Caliber: Suwa Seikosha Cal. 6159 Hi-Beat Auto
    Complications: Quickset Date Indicator (Fully Functional)
    Measured Accuracy: -47 sec/day.
    Amplitude: 171°
    Beat Rate: 36000 A/h
- Band: Original Seiko Rubber Dive Strap
- Condition Rank: (C) Fair Condition. Please See Photos and Condition Rank Guide
- Country of Manufacture: Japan

Condition Rank Guide:
-NOS: Item is in New Old Stock condition (NOS). Shows little to no signs of wear apart from some minor handling wear.
-A+: Item is in Excellent condition. Micro-scratches can be seen on the sides of the case, bezel, and/or bracelet. No pitting/gouges on the case or scratches in the crystal.
-A: Item is in Very Good condition. Minor scratches and scuffs can be seen on the sides of the case, bezel, and/or bracelet. No pitting/gouges on the case or deep scratches on the crystal.
-B: Item is in Good condition. Moderate scratches and scuffs can be seen on the sides of the case, bezel, and/or bracelet. Minor pitting/gouges may be visible on the case. One or less deep scratches may be visible on the crystal. See photos.
-C: Item is in Fair condition. Heavy scratches and scuffs can be seen on sides of the case, bezel, and bracelet. Significant pitting or gouges are visible on the sides of the case and the crystal shows multiple deep scratches
-NR: Item is in Non-Running condition. Item is not functional. For parts or repair only.