After years of resisting the ugly appeal of a Seiko Tuna, the case shape should explain the nickname, I have eventually conceded defeat and ordered one from Japan. This is a double failure as I’m not meant to be buying anything semi-expensive this year, as I move towards a mortgage splash in September or October as part of the “Big Save.” However I have compensated for my weak willedness by selling a couple of guitar bits and pieces I wasn’t using.
As you can see this is not a subtle watch. The model is officially called the Seiko Prospex Marinemaster 300 but more commonly, the SBBN015 Tuna. It’s one of those watches which has become a favourite among watch geeks but it’s not commonly seen, especially as you can only obtain it from a Japanese dealer.
The Tuna is a shrouded diver’s watch which means that the bezel, crystal and case are protected from damage by that metal shroud surrounding the upper part of the watch. The design first appeared in the mid 1970s and my model is comparatively new, being a 2010 release. I’ve been contemplating one since then. I remember there being a brouhaha about a steep price rise over the previous model but a new and highly thought of tapered bracelet with adjustable strap was the main reason. Other things such as changing the shroud screws to hex from philips and brushing the shroud rather than sand-blasting it, were only of interest in the WIS community.
The Tuna is designed as a professional diver’s watch and as such embodies particular features to take account of a harsh working environment. Clearly I’m not a professional diver, in fact I don’t really enjoy getting wet, but I do admire the aesthetics and engineering such a tool brings.
Let’s start inside the case and consider the movement. This model is a Seiko quartz calibre 7C46, which has been specially built for the range. It’s key features are it’s high torque to move those large hands and robustness While not a high accuracy movement (defined as being accurate to 10 seconds a year) it’s reported to have a far better performance than the specified +/- 15 seconds a month. The battery powers the watch for about five years, having an end of life indicator when it’s time for a replacement. As you can see from the dial, the movement has day and date complications. Part of the fun having a watch designed with the Japanese market firmly in mind, is that the day wheel contains both English and Kanji characters.
The case and bracelet are stainless steel. The case is a monocoque design, so the only way in to service the movement is through the crystal, which improves pressure and water resistance but means that battery changes are not for an ill-equipped but enthusiastic amateur. The crystal is hardened mineral, not sapphire, which raises some eyebrows at the watch’s price point but that choice was made to ensure the crystal will not shatter if hit under water. The downside is that a mineral crystal scratches more readily, there are plenty of scratched crystals viewable on online. Fitting a sapphire crystal is a popular modification.
The bracelet’s clasp is titanium and has a clever ratcheting expandable clasp which allows you to wear the watch over your wetsuit or more likely when your wrists swell when sitting at your desk in a hot office. It’s waterproof to a depth of 300 metres and uses a signed, screw down crown to maintain WR. It weighs in at 187g, 44mm diameter and is quite thick at 14.7mm. However compared to some other Tunas, that’s quite small.
I’ve always liked this particular watch, especially because of the classic appearance of the dial and bezel. The bezel is fully indiciseded and beneath the double curved, hardlex mineral dome lies the superb dial. As a working watch, the dial markers don’t have any fancy distractions such as the white gold surrounds on my Submariner. Seiko’s lume is legendary in the watch world, being the brightest and longest lasting available. The dial’s not encumbered with superfluous verbiage. The hands are functional and easily visible. I particularly like the two tone second hand. I’ve asked my seller to ensure that it hits the marks, which some quartz watches, even expensive ones, sometimes fail to manage.
I like its industrial appearance and given its size I can’t see it being one to wear every day but for weekends, holidays and fun it will be a great option to have. It has tiny lugs and these are apparently easily accessed, so changing to other staps is very much an option. The tiny lugs also mean that this big watch sits well on the wrist. At least I hope it will when it arrives in the next week or so from Japan.