Hands-on review of the Seiko Green MM300: the SBDX021 / SLA019 introduced during Baselworld 2018

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Is green the trendiest colour for Seiko this season? After introducing the green SZSC005 aka “Jade Monster” and SZSC004 aka “Green Sumo” into their ever-popular lines early this year, it came almost without surprise that Seiko introduced this Deep Forest “MM300” SBDX021 / SLA019 during Baselworld 2018, while confirming that, contrary to rumours, they have not discontinued the latest Marinemaster 300 (SBDX017) in black.

Its official name speaks all for itself: The 1968 Mechanical Divers 50th Anniversary Limited Edition “Deep Forest”. It is referenced as SBDX021 for the Japanese domestic market (JDM) and SLA019 for the rest of of the world. The lush shade of dark green is inspired from the forests of the subtropical Yakushima island, a UNESCO World Heritage site. Situated in the Kagoshima Prefecture in the south of Japan, and home to some of Japan’s oldest cedar living trees, the island is well-known for hiking, rather than diving. However, the sea around Yakushima is one of the top diving spots in the country, known for its extraordinary underwater scenes particularly made up of migratory schools of fish and colourful sea life.

Deep Forest SBDX021 / SLA019


SZSC004 aka “Green Sumo”

SZSC005 aka “Jade Monster”

The case, dial and hands

Initial reactions from Seiko fans who have seen the first pictures from news releases seem to indicate that although they love the nature-inspired vibes on the new green MM300 “Deep Forest”, most of them tend to show disdain of the “X” Prospex logo on the dial. Seiko has made an effort to align their product offerings into distinct categories.  This move to include the “X” Prospex logo into this new MM300 was probably made to fit all Seiko mid-range divers into the Prospex collection in order to avoid confusion on their various product lines. In near future, we predict that the MM1000 SBEX divers series might also get the same dial treatment to include the “X” Prospex logo on dial.


The case diameter of the SBDX021 / SLA019 “Deep Forest” sits large at 44mm and wears with a hefty 15mm thickness. With the bracelet on, the piece is seemingly designed for larger wrists, although the watch in its entirety offers good weight distribution from case to clasp for the wearer.

The dark green bezel matches the shade on the green sunburst dial, and is made from zirconia ceramic, a material known for its toughness and resistance to corrosion and rust. The lume on Seiko has always been an attractive value proposition for its divers watches and this time, the lume applied on the hands and the dial of the “Deep Forest” adopts Seiko’s latest Lumibrite which stay bright 1.6 times longer than all other previous versions.

On its caseback, it has the engraving that reads “LIMITED EDITION No.xxxx/1968”. Some collectors believe that that for limited editions from Seiko, the earlier batch of numbers are allocated to JDM pieces models. But we think the evidence is very sketchy and anecdotal, and Seiko is officially silent on the existence of a set pattern. You may want take that into consideration when you buy. So if you are looking for an earlier (smaller) number, you may wish to consider the SBDX021; if you want to try your luck on getting 1968/1968, you should be looking at the SLA019.



The movement

The movement used in the SBDX021 / SLA019 “Deep Forest” is the Seiko caliber 8L35 made by the Shizuku-ishi Watch Studio, the only laboratory in Japan that allows for a fully-integrated production of high-end Seiko movements, handmade by the very qualified watch technicians. This movement was also used in the previous MM300 and in other divers such as the Emperor Tuna models. It is often compared to the 9S55 Grand Seiko movement. The main difference being that it is not decorated for closed case back tool watches, and it does not require the need for the strict level of adjustment of Grand Seiko movements. The 8L35 (-10/+15 seconds a day) is a proven robust movement with a 50 hour power reserve, running at the rate of 28,000 bph.

According to Seiko, the “Deep Forest” is scheduled to be released in July 2018 and it will be presented with the Seiko silicon strap that can withstand daily wear-and-tear and damage from seawater, perspiration and UV rays.


Concluding Thoughts

With a limited run of only 1,968 pieces made for Seiko collectors around the world, the SBDX021 / SLA019 “Deep Forest” is definitely an attractive piece to include in your Seiko-diver-watch-snob collection, if that is a thing. However, priced at Euro 3,200, it comes up to a whooping US$4,000 or SG$5,100. At this price point, perhaps the Prospex Hi-Beat diver (SBEX series) with the 8L55 caliber may seem be a better choice simply for its movement and finishing. Nonetheless with its unique deep green hues and accents of gold on the seconds hand and dial, the SBDX021 / SLA019 “Deep Forest” will look distinctively different from your other divers, and certainly stands a deserving spot in your watch box.

Technical Specifications

Caliber 8L35 movement (-10/+15 seconds a day)
Driving system: Automatic
Vibrations: 28,800 vibrations per hour (8 beats per second)
Power reserve: 50 hours
Number of jewels: 26
Stainless steel case and bracelet with super-hard coating
Sapphire crystal with anti-reflective coating
Zirconia ceramic bezel
Screw-down crown
Water resistance: 300m saturation diver’s
Magnetic resistance: 16,000 A/m
Diameter: 44.3 mm, Thickness: 15.4 mm
Stainless steel bracelet with three-fold clasp with push button release, secure lock and slide adjuster
A silicone strap is included.
Approximate recommended retail price in Europe: 3,200 Euro
Limited Edition of 1,968

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  1. jason mirabello on

    great watch, but way too big. and the movement should be adjusted better for the price

  2. Just another guy on the Web on

    This really should not have a date. And it should be adjusted. And the price is too high. I’m sure it is wonderful in person but I get the impression that Seiko is coasting.