Marine Master

SEIKO Marine Master 300m
Caliber 8L35-0010 Twenty six jewels
Hacking and handwinding
Monocoque one-piece steel case reminisent of the original 6159-7001

This piece is known in short as MM300. Her design is an inspiration and a reissue of sorts of the original Seiko 6159-7001. Hyunsuk Seung has an extensive review of the Seiko Hi-Beat Professional 300m documented here.


This watch was shipped to me from Japan via EMS in three working days!

The monocoque one-piece steel case ensured water-tightness. Compared to a screw caseback, this will be easier to maintain and you will not have grim and grit in between the grooves and edges.

This watch sits a tad higher than most dive watches. The solid stainless steel bracelet is comfortable to wear once you have sized it correctly. Be mindful as this bracelet adopts the pin-and-collar system.

The crown is not up to mark here in my opinion. It is an unsigned crown compared to the Tuna Emperor. Likewise the crown is not the telescope type found in earlier 6309 models. At this price point, Seiko could have done a little better. But for me, this is not a show-stopper.

Solid endlinks and fat springbars.

The bracelet has polished link at 2nd and 4th link position. This is a subtle touch and does not make the watch too blingy. Hidden below the double lock clasp is the divers extension mechanism.

The clasp is thick and robust in design and yet wraps very comfortably round the wrist.

The MM300 also came equipped with a soft polyurathane waffle type rubber strap. Although a little long, it is nevertheless very easy to wear.

The trademark "Tsunami" mark on this 20mm wide rubber strap. You can use it on your Sumo too!

Overall, the MM300 is a dressier dive watch suitable with business wear. The bezel has a glossy finish and gives the watch a classier outlook compared to the other range of divers.