Monochrome Watches
An online magazine dedicated to fine watches

Seiko Prospex Diver 300m Hi-Beat SLA025 – The Ultimate Collectible Seiko Dive Watch?

Prospex steps on Grand Seiko's toes with the new vintage-inspired Diver 300m Hi-Beat SLA025.

| By Brice Goulard | 6 min read |
Seiko Prospex Diver 300m Hi-Beat SLA025 – Recreation 1968 Ref. 6159-7001

Following Seiko’s 2017 re-issue of its first professional dive watch with the SLA017, based on the 62Mas, this year the brand celebrates the 50th anniversary of another icon, the first hi-beat diving instrument ever created, the mighty 1968 Ref. 6159-7001. With this new Seiko Prospex Diver 300m Hi-Beat SLA025, the Japanese brand unveils another watch that no one can question in terms of style (it has been almost unanimously praised) at a price of EUR 5,500, which has provoked some doubts about its positioning. It’s time to go hands-on, to see the watch in the metal and to understand why this SLA025 is not your usual Seiko Prospex dive watch.

The background story behind the new SLA025

One of the stars of Baselworld 2017 was the vintage re-edition of Seiko’s first dive watch, the 62Mas or Ref. 6217-8000/1. Eagerly awaited, praised by many, decried by some as too expensive, judged by most as an ultra-faithful and superbly executed piece, the Seiko 62Mas Re-edition SLA017 was a hot topic of debate. Similar reactions occurred this year with the new Seiko Prospex Diver 300m Hi-Beat SLA025. The recipe is identical: take one of the most iconic dive watches of the brand, modernise it (just a bit), take some inspiration (a lot) and here you go… A successful talking piece.

1968 Seiko Diver 300m hi-beat 6159-7001
The original, 1968 Seiko Automatic Diver 300m hi-beat Ref. 6159-7001.

In 1968, three years after the creation of the 62Mas, Seiko delivered another impressive and innovative professional dive watch, the Automatic Diver 300m Ref. 6159-7001. This watch was not just an update of its predecessor. In just three years, Seiko had doubled the water-resistance, improved the functionality and legibility of the watch and gained drastically in precision. The Automatic Diver 300m was the first hi-beat diver’s watch on the market. Its massive size, its signature design, its iconic gilded accents; all of that fostered the legend behind the watch that is a hot item on collector’s lists.

Ad – Scroll to continue with article

The Seiko Prospex Diver 300m Hi-Beat SLA025

Seiko Prospex Diver 300m Hi-Beat SLA025 – Recreation 1968 Ref. 6159-7001

For Baselworld 2018, Seiko reintroduces the Automatic Diver 300m Ref. 6159-7001 in a slightly modernised package with a design faithful to the original 1968 piece, under the name Seiko Prospex Diver 300m Hi-Beat Ref. SLA025. This watch has, again, been a talking piece during the Basel Watch Fair; most of us praised the design and the cool overall package proposed by Seiko, yet some (without having the full story behind this new piece) questioned the positioning Seiko chose for this SLA025 and the strategy the brand tends to apply with these rare, collectible vintage re-issues – because this year’s piece is clearly stepping on Grand Seiko’s toes in terms of finishing, specifications… and price.

Before answering these entirely justified questions, let’s take a closer look at the watch itself. What is the SLA025? In short, it is a faithful recreation of the 6159-7001 – and not only in terms of design but also regarding the specifications of the watch. No negative feelings in saying that because Seiko launches exactly what the most hardcore collectors want – and this watch isn’t really made with the occasional watch enthusiast in mind.

The habillage (the watchmaking term for the external/decorative parts of a watch) of the Seiko Prospex Diver 300m Hi-Beat SLA025 is, on the whole, similar to the original 6159. Its case, with a rather massive 44.8mm diameter and a hefty 15.7mm height, is shaped with large shoulders and angular lugs. The crown is positioned, as often with Seiko, at 4 o’clock and the bezel sits high above the case. Altogether, not the best watch for a black-tie event, yet the design is just spot-on – in fact, the 1968 design was already spot-on.

Seiko Prospex Diver 300m Hi-Beat SLA025 – Recreation 1968 Ref. 6159-7001

What wasn’t visible on the official images provided by Seiko was the exceptional work done on the finishings of this case. Of course, at first you can spot two different surfaces – circular brushed on flat surfaces and polished on the flanks – very traditional for Seiko indeed. Our hands-on time with this watch gave us the opportunity to see that the case wasn’t the usual Prospex case. Nothing wrong with most of them – the Turtle or the Samurai have nicely executed cases, at least for sub-500 EUR watches.

The Seiko Prospex Diver 300m Hi-Beat SLA025 is different (thankfully, considering its price) simply because the case is finished in the exact same way as a Grand Seiko watch. This means that the polished surfaces are done by hand using traditional Zaratsu polishing, with sharp angles and perfectly flat surfaces. The Zaratsu technique (or blade polishing), which creates a distortion-free mirror finish, is an ancient method of hand-polishing used on Japanese fighting swords. Time-consuming, and only done by veteran watchmakers, the finishing of the case partially explains the price of this piece.

Seiko Prospex Diver 300m Hi-Beat SLA025 – Recreation 1968 Ref. 6159-7001

On top of this case sits a highly raised bezel with a coin-edge profile. As a professional dive watch, the Prospex Diver 300m Hi-Beat SLA025 features a unidirectional bezel, with a 60-minute insert to time events (decompression steps, diving sessions or pasta cooking time…) The black aluminium insert has a golden track and numerals, designed just like the 1968 version. The SLA025 is a monoblock watch, without a proper case back – meaning that the movement is encased from the dial side – ensuring great protection and the 300m water-resistance – again a feature found on the old 6159-7001.

Seiko Prospex Diver 300m Hi-Beat SLA025 – Recreation 1968 Ref. 6159-7001

As for the dial, Seiko brings back the flair of Reference 6159-7001 with a matte black “gilt” dial – meaning that inscriptions, tracks, hands and applied indices are gold-coloured or gold-plated. Compared to the old version, the differences lie in the details. Hands and indices, as well as the tracks, are very close in shape to the 1968 model, but their execution is lightyears ahead in terms of quality. If you look closely at the hour hand, you’ll see the typical Grand Seiko large polished bevel on the sides. A similar attention to detail has been given to the date window. Precise, clean, detailed, surprising for a Prospex watch… but desirable.

Seiko Prospex Diver 300m Hi-Beat SLA025 – Recreation 1968 Ref. 6159-7001

The link with Grand Seiko doesn’t end here. Inside the case is Calibre 8L55, a hi-beat (5Hz or 36,000 vibrations per hour) movement developed especially for diving purposes. What’s more interesting with this movement is that it is a slightly simplified and less decorated version of the Grand Seiko calibre 9S85. If a bit less attention will be given to the adjustment and to the finishing, what remains is a high-end movement with a 55-hour power reserve, 37 jewels and very decent accuracy.


What conclusions can we draw about this 1,500-piece limited edition SLA025? Well, in short, we’ve been captivated… The watch is impressive on all levels: the finishing of the case, the faithfulness of the design, the beauty of the mechanics, and the surprising overall execution for a Prospex watch. On this front, Seiko doesn’t disappoint making the Seiko Prospex Diver 300m Hi-Beat SLA025 a true collector’s piece.

Seiko Prospex Diver 300m Hi-Beat SLA025 – Recreation 1968 Ref. 6159-7001

The Prospex Diver 300m Hi-Beat SLA025 should be seen as the über-Prospex or a wannabe Grand Seiko!

Now to address the issue of its price tag. The Prospex concept (affordable, reliable, professional watches) isn’t entirely at work here, and it is true that at EUR 5,500 the price has raised some eyebrows. Certainly, the execution of the case, the beauty of certain details (the hands for instance), the scarcity of the watch and the prestigious movement help to explain the price. This watch could almost be a Grand Seiko and in that sense, it plays in another league.  This watch should be seen as the über-Prospex and thus, it has arguments to fight against established Swiss brands. And remember that the Grand Seiko hi-beat divers SBGH255 – SBGH257 are priced over EUR 12,000. Maybe the Seiko SLA025 isn’t that expensive after all…

More details on

7 responses

  1. Hi Brice,
    thanks for sharing.
    There’s not much to say concerning the watch itself: a superb piece in my opinion.
    Concerning the price issue, it can be perceived as an issue only if you consider it as “Prospex” and compare it to the other standard Prospex. If you take the watch for itself instead, the price is selfexplaining. How many other brands can offer an high beat with high accurate finishing and tech features as a monobloc case and 300m for such price (not to mention the heritage behind the piece) ?

    Just my two cents,

  2. “captivated”… Well, perhaps, but perhaps not. This could easily be the Seiko for me, BUT,

    – A $5,500 watch with a $5 strap. Compared to others > $5,000?

    – Limited edition Japanese watches are notoriously unobtainable outside Japan. I understand the entire marketing-/business-plan of it, but still, this ain’t no Rolex.

    – Accuracy is where things get interesting. Accurate compared to what?

    – Execution of the case and hands – compared the what; Tudor, Oris, Nomos?

    BOTTOM LINE: >$5k you are entering the ring with some Swiss/German heavy-weight boxers – better have your mouth-guard handy.

    That said, 36k vph with 55h of power, is not an $80 Seiko 5. Plus, what is more captivating than staring at a smooth running seconds hand, instead of telling the time…

  3. Less attention given to adjust and finishing but you get decent accuracy all for E5500. Seiko must be kidding?! Compared to its lower priced offerings, this watch doesn’t begin to justify the cost.

  4. If you’re going to step on some Swiss toes, best to have a slightly heavier foot at this price point by offering at least a 600 meter dive rating.

    Grand Seiko is obviously not a concern so let’s swing for the fences and offer an option to the rubber strap.

  5. I’m in love with this watch and want one bad. The JDM variant – SBEX007is already available for pre-order, and it’s around US$5,100 with current exchange rates. Still waiting for word from my local dealer on the International SLA025 variant. Would prefer the International version due to warranty – 3yrs vs 1yr, international coverage vs JPN-only – even if JDM versions tend to be more desirable among Seiko collectors.

  6. I am delighted to say I am wearing the SLA025 as I type. I have fine wrists and am surprised how comfortable the watch wears. The watch is only an occassional wear for me and never with a suit: more likely to go with something like a Navitimer. One of my favourite elements of this watch is that it is effectively invisible; only on a few occassions has a fellow collector passed comment but for me I look down and see the quality of the quality of the polish and detailing. In conclusion, I have never regretted the purchase or the price I paid.

  7. One thing you have to say here – no one is going to steal it from your wrist in Paris or downtown London 😉

Leave a Reply