REVIEW: Seiko Prospex SRP775 Diver

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Seiko is not only the oldest Japanese watch manufacture – with horological expertise dating to 1892 – they also have an incredibly strong diving heritage.

In 1965, Seiko released their first dive watch, the 150 meter water-resistant reference 62MAS-010. Many dive watch models followed over the years. And not much has changed in that regard, as Seiko continues to make numerous dive watch models across a broad range of price points.

For this article, we will focus on the modern SRP775 Prospex Diver, based on vintage reference 6309 that was produced from 1976-1988.

Introduced at Baselworld 2015, the Prospex SRP775 Diver, nicknamed the “Turtle,” shares the original 6309’s cushion-shaped case design and has approximately the same dimensions. In fact, the hands, bezel, crown – and even the embossed logo on the back – are virtually the same. There are, of course, differences. For instance, the water-resistance rating has been improved, the movement has been upgraded, the use of a lollipop on the seconds hand has remained but its implementation is different, which we will explain further below.

Seiko-Reference-6039-divewatch.pngSeiko reference 6039 from original Seiko catalog

The dial

The Prospex SRP775 features a matte black dial with gilt print and gold plated Lumibrite hour markers. The large hour and minute hands are centrally mounted, and feature gold-plating that complements the gilt dial and bezel. The design of the luminescent sword-shaped hour hand and arrow-shaped minute hand is copied directly from the original 6309.

The centrally mounted second hand, however, has changed. For this particular version, it is baton-shaped on the front with a lollipop-shaped, opposite of the where the lollipop is on 6309s. The front half of the hand is gold-plated and the back half is matte black lume inside the circle. This design looks great, although in low-light situations you would expect the luminescent tip to be on the opposite end like the original. Not a big deal while diving as you are timing minutes underwater, not seconds, and so as long as you know the watch is still ticking, that is what matters in respect to seconds hand.

The rectangular day/date wheel opening in the dial at 3 o’clock was previously somewhat flat, but now that the edges of the opening are beveled date, it appears more three-dimensional.

According to Seiko, there are different date wheel options, depending on the market, the retailer, and so forth. This particular version features the Spanish acronyms for the weekend and English acronyms for the weekdays. “SAB” in blue is short for Sábado (Saturday) and “DOM” in red is short for Domingo (Sunday). The five weekdays are represented by “MON-FRI”, in black.

While this is not the brightest application of lume I have ever seen on a watch, the luminescent level of the hands and markers is quite generous and very intense. Not to mention, the large markers and hands make the dial incredibly easy to read at a glance, day or night.

The printed script on the dial reads “SEIKO” in gilt lettering at 12 o’clock, and at 6 o’clock, the new Prospex “X” logo, with “AUTOMATIC DIVER’S 200m” just below that. Overall, the printing on the dial is executed very elegantly in my opinion. Too much writing always seems to add clutter.

A black flange, with gilt graduations, is angled at a 45-degree angle and marked with 60 indexes to indicate the seconds or minutes.

Protecting the dial is Seiko’s proprietary Hardlex mineral crystal. The crystal is flat and is recessed just below the bezel, adding a level of armoring compared to a crystal the protrudes above the bezel.

Seiko-PADI-SRPA21-Turtule-Diver.jpgSeiko PADI SRRPA21 Diver “Pepsi” Bezel which we wrote about HERE

The case

The cushion case of the Turtle is part of what gives the watch its distinctive look. It’s also where the unofficial nickname “Turtle” is derived from.

For the 1970s and 1980s, when the original 6309s existed, a 44 mm diameter case was big. It is still big today, but the size is much more prevalent nowadays. For reference, Omega made a variety of similar cushioned-shaped Seamasters around the same time period, and those typically measured under 40 mm in diameter, including the crown.

The 120-click unidirectional rotating bezel (the original 6309 has a 60-click bezel) features a black aluminum insert with a gilt dive scale and a triangle with a luminescent dot at 12 o’clock. The black finish of the bezel features a grain texture that looks particularly stunning with the gilt numerals and graduations. Moreover, the two rows of polished, knurled grooves along the outer flange of the bezel stand out particularly well, especially because the entire top of the case has a contrasting circular brushing.

“The cushion case of the Turtle is part of what gives the watch its distinctive look. It’s also where the unofficial nickname ‘Turtle’ is derived from.

On the back side is a solid steel screw down caseback with Seiko’s Tsunami “Air Diver” embossed motif, which is exactly the same as on the 6309, even though the caseback perimeter is slightly different.

The crown is mounted at 4 o’clock, and is 7 mm in diameter, with ridged edges and a polished cap with no logo. Naturally, it screws down as this is a 200 meter diver, and so there are also gaskets sealing the crystal, caseback, and crown.

With the included steel bracelet, the watch weighs in at 181 grams. Head only the watch weighs 92.3 grams. The bracelet alone weighs 88.7 grams. That is a bit much. With a nylon, NATO strapped to the watch it barely weighs over 100 grams total. Wearing it with a lighter strap is more comfortable that the bracelet for me, but the bracelet aesthetic makes it worth the extra weight.


For the best of both worlds, keep a strap removal tool and extra straps handy, as the case features pierced lugs, allowing easy bracelet/strap changing compared to watches without pierced lugs, or a quick-change system.

One notable difference in the dimensions of the 6309 and SRP775 cases is that while the diameter is approximately the same for both, at 44.5 mm in diameter – the new version is about half a millimeter thicker, at 13.5 mm. Lug-to-lug length is 47.5 mm. Interhorn width is 22 mm, and the bracelet tapers down to 20 mm at the clasp. The three-way folding clasp has a pressure closure with push-button locking so it does not come undone while underwater during a dive. The bracelet is stainless steel with a brushed finish contrasted by two polished stripes down the center. It has push pins with collars on one side for resizing by adding or subtracting links. There is also an extension function so the bracelet can be fitted over a wetsuit.


The movement

The Seiko Prospex SRP775 Diver watch is powered by the caliber 4R36 automatic movement which beats at 3Hz (21,6000 kph). While this is the same rate as the caliber 6309A, it is a more modern movement in that it features hand-winding and the ability to hack the seconds hand for precise setting of the seconds hand, which caliber 6309A does not. There are also 24 jewels as opposed to 17 jewels, which along with other evolutionary upgrades, presumably make the caliber 4R36 more reliable.

Caliber 4R36 is made in Japan and features a 41-hour power reserve. Although the movement is not visible, like its predecessor it is protected against shocks and magnetism and features an industrial finish that keeps the cost down. It is pragmatic with little concern for aesthetics, which is completely fine as this is a lot of watch for the money and additional movement finishing, which would be hidden anyway, and would just raise the price.



Despite the relatively large size of the case – which is not enormous nor diminutive – it wears well, particularly because the crown is located at 4 o’clock. If the crown was positioned at the traditional 3 o’clock location it would likely dig into your wrist more. With the metal bracelet attached, the watch weighs 181 grams, which is quite heavy but not unprecedented for a watch with a steel bracelet. Nevertheless, I did find the heft to be a little uncomfortable at times. The simple solution, if the bracelet feels too heavy for your liking is to switch to a strap. I swapped out the 88.8 gram steel bracelet for a 12.1 gram Nato strap and instantly shaved off 76.7 grams, bringing the total weight down to just 104.3 grams. Since then I have worn the watch a number of days with the Nato attached and it is noticeably more comfortable in my opinion.

One thing that really stands out to me about the Turtle is the curvature and polishing of the case flanks. When you view the profile of the watch, on your wrist you really notice the beautifully polishing smooth yet angles of the case. It is reminescent detailing you see in the case of the Grand Seiko GMT I reviewed earlier this year. Details like that are what make this watch such a success, and a step-up from something like the Seiko SXK007, which has a very similar dial and aesthetic, but not quite this level of craftsmanship.

Overall, while there were numerous iterations of the 6309 during its decade-plus existence, including many variations to the dial, as well as some later models with slightly slimmed down cases. This is a very faithful re-issue of the 6309 in many ways, and that is a good thing. Furthermore, the watch is more accessible than almost any other dive watch on the market (with the exception of other dive watches from Seiko, such as the Monster or SKX007K). That is because when you have the economies of scale that Seiko has, you can offer more watch for less.

The Seiko Prospex SRP775 features a gilt dial and steel bracelet, for $495. There are two other variants to choose from, including the SRP777 with a black dial (non-gilt) and a black rubber strap for $475, and the SRPA21 which has a blue dial and blue and red bezel “Pepsi-bezel” on a steel bracelet for $525. There is also a fourth model, reference SRP773, with a blue dial and bezel, which is available internationally.