The Seiko Samurai Prospex – Ref: SRPB51
- MJB
- Aug 20, 2018
- 4 min read
So, you’ve taken my advice and bought yourself a couple of Seiko Automatics, the SNZF Sea Urchin and the mighty SKX, good decision, well played. What’s my next move? I hear you ask.
Well, first of all, if you don’t want to find yourself in trouble with the other half for owning fifteen Seiko divers, that apparently, seem to be the same watch with a different colored dial, then you should stop reading this blog. But if you’re willing to accept the grief, let’s proceed.
Truthfully, there’s a few options to consider if you’re looking to go a step further in the Seiko diver series. Like many others, you might find yourself leaning towards the Turtle Reissue (SRP77X), or even the PADI special-edition (SRPA21), a modern throwback to the iconic Seiko 6309 Turtle. The original Turtle 6309 remains one of the most popular vintage divers to date, so no real surprise Seiko decided to drag the old girl out of retirement and give her a new shot of life.
The Sumo (SBDC031), or its deep blue counterpart the intelligently named Blu-mo (SBDC033), is another great choice. We’re talking about a seriously well-equipped, beautifully finished watch, with a price tag that never goes out of style.
Seiko actually made two generations of the Sumo, so if you are in the market just make sure to do your homework. The 001 was the original reference, however this was discontinued when Seiko introduced the Prospex line, something we’ll touch on again shortly. The replacement was the 031 which, to all intents and purposes, is the same watch with some very minor cosmetic changes. Essentially they wanted to stamp the Prospex logo on the dial to bring it in line with the rest of the series, and give the lume a quick upgrade in the process.
Today however, it’s the turn of the Seiko Samurai (SRPB51) to go under the microscope. The SRPB51 retails around the £350 mark, but you’d be able to pick one up second hand for £250-275 if you're lucky.

First off, Prospex, what is it, and why should I care?
Frankly, the term itself is pretty irrelevant, just a corporate buzz-word to rope in some punters. Pro-spex, in Seiko speak, literally means Professional Specification. Those deemed worthy of this great honor receive the mark of the beast, the familiar Prospex 'X', stamped front and center on the dial. Basically it's Seiko's attempt to elevate the Prospex line-up above the more entry level 5-sports and standard diver series, sorting the men from the boys.
Credit where its due, there are a few noticeable upgrades on the Samurai, in comparison to the likes of the Urchin and SKX. The 4R35 movement is a cut above the 7s26, supporting hacking and hand winding. To be honest not having these features wouldn't be a deal breaker for me, the 7s26 is still a cracking movement, but they are well received on a watch that will likely get less wrist time than the everyday beater. The 4R35 runs at 21,600vph, contains 24 jewels, and claims a power reserve of 41 hours. According to official figures the accuracy should sit around -35/+45 seconds per day, but I'm pretty convinced that's Seiko playing it safe. The solid end-links are a nice touch too, I cant deny it frustrates me that the SKX wouldn't be given these as standard.
For me though, it's the overall finish on this watch that sets it apart from the rest, and ultimately makes the Samurai a very interesting value proposition. It looks, and feels, expensive. This isn't a cut and shut job, grab a few parts from other Seiko models and whack them together, in some sort of twisted Frankenstein-diver fashion. Seiko have taken their time with Samurai, and it really shows through the craftsmanship and cleverly thought out design. Each time you throw this watch on you'll find something new to love about it.

As the name would suggest, the Samurai is sharp, angular, and generally pretty intimidating ... well, sort of. One of the most refreshing things about this time piece is the unconventional design, so many modern dive watches fall into same trap, unimaginative, overused and down right boring styling. Not the Samurai, the bezel and crown are knurled, the hands look like something from an ancient Japanese weapons cabinet, and the patterned dial is sharper than a bag of throwing stars. It's possible I'm getting carried away here, but you get the gist.
The bracelet is comfy and well designed too. Granted, from some angles it does look pretty similar to some of the less expensive models, but on closer inspection the subtle combination of brushed and polished stainless steel adds to the overall premium feel. The case back is, as usual, a work of art, adorned with the Seiko tidal wave, serial numbered, and even gets the same Prospex 'X' treatment as the dial. At 44mm it's fairly chunky and, certainly with the stainless bracelet as opposed to rubber, has a bit of weight behind it. Seiko have definitely found the right mix of presence on the wrist, without being over the top and cumbersome.

It's a superb watch, and as always, the performance and styling go well beyond the price tag. If you are looking for the next step up in your collection, give this a go, you wont be disappointed.
The Urchin Report.
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