Tuesday, October 20, 2015

Seiko Prospex 200m Diver SRP637 (or SRP637K or SRP637K1) Shrouded Black Monster (a.k.a. Monster Tuna) - A modern transformation of the original Monster to something bigger and stylish, A Review

I just love the metallic shrouds on high end Seiko dive watches. I have collected three shrouded diver examples from Seiko over the years; the SBDX011 ‘Emperor Tuna’, the SRP653 ‘Baby Tuna’ and the SUN019P1 'Vader-Tuna-Turtle' (although I got another shrouded watch from Seiko, the SBDC011 Fieldmaster is not a diver hence the reason I excluded it from the list). A few years ago, Seiko incorporated the shrouded concept to the Monster series with the launch of the SRP233, SRP234 and SRP236. However, what put me off from looking into that series further was the fact that the shroud was made out of plastic. Nevertheless, the price point and size were just nice to be able to be an affordable and wearable wristwatch to many people.


This year, Seiko answered the request by its legion of fans to come out with a new series of shrouded Monsters by introducing the SRP637, SRP639 and SRP641 series. This time around the shroud is made out of metal! What makes it even more special is that it has been upgraded to be under the Prospex series of professional tool watches.

I immediately made the necessary inquiries to get the best price possible from some of my trusted suppliers. However, the demand was so great that the initial consignment for Malaysia was sold out in a matter of weeks. As it was also the same time since the introduction of GST into the country, I was not willing to get a unit from my overseas suppliers as I was not comfortable yet with the new custom rules and procedures for imports. So, I waited for the supply to catch up with demand.

After a few months I finally got my hands on the Seiko SRP637. The watch is sizable. It comes with a diameter of 47.5 mm (excluding crown) and a lug-to-lug distance of 50 mm. Coupled with a thickness of 14 mm, the watch makes it presence obvious on one’s wrist.



This particular mode that I got, the SRP637, is an all stainless steel construction including the bracelet. The polished 316L stainless steel is a magnet for fingerprints. I would have preferred another option of brushed steel finishing instead. Nevertheless, if you decide not to use the standard bracelet, the lug width is 22 mm and this opens up a myriad of strap options. This is why I chose the SRP637 instead of the other two types in the series. The SRP639 and SRP641 only come with rubber straps. With the SRP637, I have the option of the bracelet as standard. It is always cheaper to get a strap than to get a bracelet.

The Buying Experience

I got the watch from AWG in Mid Valley Megamall in Kuala Lumpur. The listed price was RM2,199. In January 2015, the SRP637 was listed at RM1,680. This means the price has moved 31% (if excluding the effect of the 6% GST into the price, a net increase of 25%). I should have been more persistent back then. The transacted price was RM1,588 a discount of approximately 28%. Anyway, the shop did give me a free gift of a multi-tool penknife from Luminox.



The shop also gave a limited edition box instead of the standard watch box as well. Despite the watch being part of the Prospex series of professional tool watches, I was told by my dealer that Seiko (or is it Seiko Malaysia) uses the standard presentation box for the SRP637. If this is true, I suggest Seiko use a more appropriate presentation box with at least the Prospex logo on it. The photo below on the right shows the manual and guarantee documents.



The Reveal

The first impression that I got when I lay my eyes on the watch is how utilitarian it looks. A non-nonsense kind of watch, the lines and planes on the casing and bracelet are direct and purposeful. I have read from some reviewers negative comments regarding the design of the bracelet links. The H-links design on the bracelet was deemed to be too simplistic and does not “enhance” the watch.

My view is the opposite. We must take into account the design philosophy of the watch. As part of the Prospex series, the watch is designed to fulfill a specific professional task. In this case, a diving watch down to a maximum depth of 200 meters. Styling and the need to keep up with fashion are not part of the product specifications. The designers in Seiko needed a watch that can fulfill all the professional tasks it was original designed for.

The standards the designers were working from are more exacting than the internationally accepted ISO6425 standard for dive watches. The SRP637 surpasses the international standard by a mile.

The dial is all black. The date and day window is located at the 3 o’clock position and partially replaced the 3 o’clock marker. Almost all hour markers are trapezium shaped with the 6 o’clock and 9 o’clock markers made larger (despite the 3 o’clock marker position been displaced by the date and day window, Seiko decided to add a small thin strip of luminous marker at the corner). The 12 o’clock marker is pyramid like with a line in the middle of it. All the markers have been liberally laced with LumiBrite paint.

The hour hand is an arrowhead that has a line in the center while the minute hand is the broad sword type. Both are also fully painted with LumiBrite. Meanwhile, the second hand is thin with a small triangle. Only the second half of the second hand is painted with LumiBrite.

There is a slopping chapter ring surrounding the dial and this is where the minute markers are painted on. At the inner-end of the every hour markers, there are number ‘05’ to ‘55’ (no numbers are printed on 12-, 3-, 6- and 9 o’clock positions). A number of reviewers noted some form of misalignment between the markers on the chapter ring and the markers on the dial. In my particular example they aligned correctly. 

On the dial itself, there are five lines of text or images. The first is the ‘SEIKO’ brand at the top half of the dial. The other four lines are at the bottom half; the first (top to bottom) is the Prospex logo, the next is the word ‘AUTOMATIC’, then comes the text ‘DIVER’S 200m’ and finally (in very small font) the words ‘4R36- 0384 R 2’.



The bezel is unidirectional counterclockwise with 120-click gradation. There is a healthy clicking noise when turning the bezel. The sides of the bezel have saw-tooth-like serration for gripping. Due to the protective shroud, one has to grip it at the Northeast and Southwest quadrants only. Another option is to grip it from the top. Since the minute and hour markers (alpha-numeric) are cut into the bezel, it does afford some grip. All the cut groves on the bezel are painted with black paint. The required lumed pip is set at the 12 o’clock position.

The crystal covering the dial is Hardlex, a proprietary crystal made by Seiko. A flat glass, it sits at the same level as the inner edge of the bezel. Since the bezel slops slightly inwards (the other edge is higher than the inner edge), the crystal has that added protection against glancing blows.

Below are just some examples of other Seiko dive watches that I own. A number of reviews mentioned that the SRP637 has taken some design cues from other dive watches. However, in the pictures below you can clearly see that the DNA of the SRP637 is predominantly the original Monster SKX779 (middle right). The bezel and hands looks uncannily similar as well as the markers (albeit the different way up). Meanwhile, the shroud is similar to the SRP653 (top left).



The shroud is thick and does give confidence to be able to absorb all kinds of punishment that one could subject the watch too. The shroud is fastened to the main watch case with three stainless steel screws, two on the left of the casing (distributed evenly from one another and the lugs) and one on the right side of the casing above the crown that is located at the 4 o’clock position.

The bezel is a slightly above the edge of the shroud. Although the likelihood is smaller, the bezel can still be impacted by a glancing blow. In my view, it would be better for the shroud to be just slightly higher than the top of the bezel for maximum side protection.


The screw-down crown is located at the 4 o’clock position. Set in a small recess inside the shroud, it provides a slightly better protection than the original short shoulders provided for in the original Monster SKX779 (see top group of six photos, middle right). Also note that unlike other Prospex divers, Seiko kept the top of the crown bare.

From the photos above, you can also see the pass-through pinholes for the main lug pins. This helps bracelet or strap replacement. Also note the lugs are curved downwards. This curvature enables the watch to be much more wearable for those with smaller wrists.


The lug width for the SRP637 is 22 mm. The standard bracelet that comes with the watch is similar is shape to the bracelet on the original SKX779. It is tapered to 20 mm at the clasp. This bracelet has four micro-adjustment slots as well as a diver’s extension mechanism in the clasp. The clasp has Seiko’s standard 3-point safety system. The ‘SEIKO’ brand is prominently stamped on the safety lock.

A new modification that Seiko introduced for this bracelet is not obvious as it is hidden from view. It is a new pin-collar system to attach the various links on the bracelet. Whereas in the original bracelet there were two collars for every pin, in this new version, only one collar is required.



The case-back is a solid screw-down plate. The famous tsunami logo for Seiko diver’s watch (actually, this is a misconception. The true focus of the image is the wind that’s whipping such a wave – the Divine Wind – Kamikaze).

The engine powering this watch is the Seiko 4R36 automatic caliber. Ticking at 21,600 bph (or 3 hertz), this 24 jewels movement has hand-winding and seconds-hand stop function capabilities. This movement is capable of 41 hours of power reserve.



Like the Monster of old, the brightness and sustainability of the luminous paint remains legendary. Although there are no literature that suggest the type of paint used, based on the colour of the paint, I hazard a guess that this is the latest recipe of the LumiBrite. Above is a picture of the illumination after a short stint in the sun and in a relatively bright room.


Based on dimensions, the SRP637 is a relatively large watch. However, the shape of the lugs does make it easier to wear for those with smaller wrist sizes. Nevertheless, if you have worn other shrouded divers from Seiko such as the SRP653, SUN019 and SBDX011, the SRP637 feels small.

The shroud is not a straight wall around the watch but angled. This has the benefit of limiting the possibility of snagging on clothing etc. I have worn the watch with my formal shirt to office and it is not a problem at all. In fact, the watch feels at ease in all kinds of environment.

Overall, I am satisfied with the watch. I can’t find anything wrong to highlight apart from the pricing. Over the last few years, I started to see a trend by Seiko to upgrade series of watches to that of the Prospex hence justifying a higher price point when the only change that is noticeable is the Prospex logo on the watch. I do suggest that Seiko re-look into this policy. Remember the legions of fans out there that can only participate in watch collection because Seiko is able to offer quality mechanical watches at such affordable prices. Don’t alienate your fans just for a few extra bucks. China is coming up in the world of horology and Chinese made watches (the quality is improving by leaps and bounds) can easily fill the void if Seiko decide to shun the ‘low-end’ market.



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