Monochrome Watches
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Seiko Prospex Black Series Limited Edition SLA035J1 & SPB125J1

The new MM300 and the Sumo get a full black attire with the Prospex "Black Series".

| By Brice Goulard | 5 min read |
Seiko Prospex Black Series Limited Edition SLA035J1 and SPB125J1

In recent years, Seiko has demonstrated that it doesn’t shy away from bold and colourful creations, even in its technical and professional-oriented Prospex collection – Prospex meaning “Professional Specifications”. Apart from the traditional black and blue divers, the brand offers cool colour schemes in its limited-edition models, such as the “Twilight Blue” SPB097J1 or the “Dawn Grey” Europe-Only watches. Today, it is two of the brand’s most acclaimed models, the Sumo and the successor to the MM300, that get a different visual approach. Meet the new Seiko Prospex Black Series Limited Edition SLA035J1 & SPB125J1.

Seiko’s reputation for dive watches does not need to be demonstrated, and that is true across all ranges, from accessible watches like the Turtle or more high-end pieces like the recent SLA033 or the LX Line with Spring Drive movements. Today, it is two of the most emblematic Seiko dive watches that are used as a base for a series of limited editions with one common trait: a full black attire with coloured accents on the dial. One is based on the mid-range Prospex Sumo, a watch that has recently been updated. The second is based on the successor to the famous MM300. Indeed, this watch (ref. SBDX001) was removed from the collection a couple of years ago. However, Seiko has replaced it with a new model under reference SLA021 – with the same visual concept and a higher-end movement.

These two watches in the Seiko Prospex Black Series (note that a third one is also included, a Solar chronograph under reference SSC761J1) have been updated from the standard steel models with a hard black coating, a matte black dial and coloured accents. Both are worn on silicone straps instead of the usual steel bracelets. Let’s take a closer look at each model.

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Seiko Prospex Black Series SLA035J1

The first model to be included in this “Seiko Prospex Black Series” is based on the recently introduced SLA021. This watch can be seen as the successor to one of Seiko’s most famous dive watches, the Marinemaster 300 ref. SBDX001 or SBDX017. The new version is more of a visual and technical update than an entirely new watch. Knowing that the discontinuation of the MM300 ruffled some feathers, Seiko introduced a new model to replace it.

Seiko Prospex Black Series Limited Edition SLA035J1

This updated model retains the massive monobloc case of 44.3mm with a raised unidirectional bezel and typical coin-edge profile. The case also keeps its signature angular shape, with sharp lugs, now finished with the Zaratsu polishing technique. The main update concerns the bezel, which is now made of ceramic. Inside is Seiko’s calibre 8L35, based on the Grand Seiko 9S55 – which was already used in the SBDX017. Compared to the previous model, the dial, the hands and the 60-minute scale have been slightly redesigned.

Seiko Prospex Black Series Limited Edition SLA035J1

Today, we have a new version of this watch, with a full black colour scheme. The new SLA035J1 has a steel case that is both polished and brushed, now blackened with Seiko’s hard-coating. The bezel, crown and caseback are similarly finished. The case is water-resistant to 300m and a sapphire crystal protects the dial.

Regarding other updates, we can see that the base of the dial remains unchanged, with the exception of two details: both the WR rating and the seconds hand have been painted red, while they are gold-coloured on the standard steel version. The Lumibrite used on hands and indexes also appeared more cream-coloured than on the steel versions. No updates inside, the Seiko Prospex Black Series SLA035J1 has the in-house, automatic calibre 8L35 with 4hz frequency, 50-hour power reserve and +15 to -10 seconds per day accuracy.

Seiko Prospex Black Series Limited Edition SLA035J1

The SLA035J1 (also named SBDX033 in Japan) is worn on a black silicone strap with a blackened pin buckle. It is a limited edition of 600 pieces available from March 2020. It will be priced at JPY 300,000, and an approximate price of EUR 3,100 in Europe.

Quick facts: 44.3mm diameter x 15.4mm height – 50.5mm lug-to-lug – stainless steel with hard black coating – sapphire crystal – unidirectional ceramic bezel – 300m water-resistant – calibre 8L35, automatic, in-house, 50h power reserve, 4Hz, 26 jewels, HMS and date – black dial – silicone strap – ref. SLA035J1 – limited to 600 pieces

Seiko Prospex Black Series SPB125J1

The second model in this “Seiko Prospex Black Series” sub-collection is based on the praised and relatively accessible Sumo model, a watch that has been updated in 2019, with the addition of a sapphire crystal and a new movement. Visually, the DNA of the Sumo is still present though, with only minor updates on the case, dial and bezel.

The Sumo is a robust mid-range model in Seiko’s Prospex line. Compared to the entry-level Turtle and Samurai, it offers a better finishing overall, a more robust bracelet, a sapphire crystal and a more precise movement from the 6Rxx series – but still the same 200m water-resistance.

Seiko Prospex Black Series Limited Edition Sumo SPB125J1

For the occasion of this “Prospex Black Series”, the brand brings here reference SPB125J1, with multiple visual updates compared to the classic steel version. First of all, all the external parts have been blackened with a hard coating. Here too, we have a black silicone strap instead of the steel bracelet. The bezel’s insert, in anodised aluminium, features a two-tone scheme, with the first 20-minute area in dark grey, the rest being classically black. The shape of the case, with its twisted lugs and its 45mm diameter, remains untouched.

The dial has undergone the greatest evolution on this SPB125J1. If the watch retains the matte black background of the steel model SPB101J1, it now features beige-coloured Lumebright on indexes and hands, instead of pure white. The minutes hand is also different and is painted in bright orange, while the hours and seconds hands are black. Inside ticks the calibre 6R35 with 3Hz frequency, 70-hour power reserve and +25 to -15 seconds per day accuracy.

Seiko Prospex Black Series Limited Edition Sumo SPB125J1

The Seiko Prospex Black Series SPB125J1 (or SBDC095 in Japan) will be a limited edition of 7,000 pieces, available worldwide from February 2020 and priced at JPY 90,000 or EUR 829.

Quick facts: 45mm diameter x 12.9mm height – 52.6mm lug-to-lug – stainless steel with a hard black coating – sapphire crystal –  unidirectional aluminium bezel – 200m water-resistant – calibre 6R35, automatic, in-house, 70h power reserve, 3Hz, 24 jewels, HMS and date – black dial – silicone strap – ref. SPB125J1 – limited to 7,000 pieces

More details at the dedicated pages at

6 responses

  1. Stupid question, I know, but……. why the hell is it a limited edition?? Of course to charge way over, but… why do this, why not just make it a watch to wear… arrrgghhh…

  2. Where are the shots of the back of the watch? Too often the rear of the watch is omitted. Big mistake.

  3. @Warren – as you can see, these are not our photos but official press images. And Seiko doesn’t provide caseback images…

  4. Guy, what do you mean Seiko is not Seiko anymore? What happened two years ago? I have only been follwing watches for about two years max, so I don’t know… I don’t know, I seem to like a lot of Seiko offerings, newer and older, not all, but a lot, in the Prospex diver range, or in the Presage range. Besides, I have emotional childhood attachment to Seiko. What happened two years ago? And do you really not like any Seiko now? Why?

  5. @Maciej… no worries, JAGOTW is our resident keyboard warrior with rather stiff opinions and equal language. I assume he’s referring to Grand Seiko being positioned as a separate brand.

  6. I’m like maciej, I got really into watches a few years ago. But these remind me of my seiko5 I got last year. They are very similar

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