The SPB455, part of the trio launched for Seiko's special centennial, is a diver’s watch designed with subtle yet impactful upgrades that enhance both its aesthetic and technical appeal. It features a 40mm case diameter, a 46.4mm lug-to-lug length, and a slim 13mm thickness, making it compact and wearable without sacrificing presence on the wrist. The stainless-steel case is paired with a slim, unidirectional aluminium bezel, colour-matched to the dial, and laser-engraved minute markers for longevity. Under a flat sapphire crystal dome sits the charcoal-grey sunburst dial, accented by satisfyingly chunky and rectangular gold hands and markers, a nod to Seiko’s long history of watchmaking advancements.  

There's been an unmistakably Japanese flair when it came to the product design challenges of this timepiece—something that the core team from Tokyo's Ginza headquarters shared with us back during the watch's release in June. Perhaps my favourite one is the ambitious jump up in water resistance from 200 to 300m; a task accomplished by gradually adjusting case angles from within the watch's internal chambers, resulting in a retro-revival divers' that wasn't just more capable but was slightly thinner and more wearable too. 

Apart from its striking colourway, the SPB455 comes with an extra NATO-style strap made from recycled polyester, crafted using the traditional Japanese Seichu braiding technique. This method interweaves threads in a way that creates tiny gaps for airflow, keeping the strap cool and dry—even in Mumbai’s steamy mid-monsoon. I ditched the steel bracelet for the strap during that period, and it turned the watch into a comfortable daily driver, perfect for long writing sessions and rain-soaked motorcycle rides. The strap’s texture and sheen nod to kimono cords, giving the watch a distinctly Japanese touch. Plus, it’s tough—four times stronger than standard Seiko fabric straps—making it ideal for heavy-duty use. A ‘SEIKO’-marked fastener and a subtle grey-on-black wave pattern beneath the strap mirror the closed caseback’s engraving, adding even more flair. 

At the heart of the SPB455 is Seiko’s in-house Calibre 6R55, a reliable automatic movement with a 72-hour power reserve. This movement operates at a frequency of 3Hz, offering solid everyday accuracy, and its inclusion marks the first time the Calibre 6R55 has been used in the Prospex collection since its launch last year. The round date window, placed between the 4 and 5 o’clock positions, is subtly integrated to maintain the watch’s symmetry. The window seamlessly melds into the charcoal-grey dial, and the decision to keep the screw-down crown at 3 o'clock ensures that the new design doesn't stray too far from its 1965 inspiration. 

In summary, the SPB455 is one of this year's highlights from the Japanese marque, and offers an accessible, though subtly striking entryway into the world of diving watches. Though I expect it to butt heads with the likes of Tissot's Seastar and the Doxa 200T ranges, the Seiko, almost uncharacteristically oozes a lot more character than its rivals at this price point and possesses a much more timeless appeal in today's era of tasteful ’50s and ’60s homages.