The Seiko Prospex "Sumo" – before it was known as such – was released in 2007 as a mid-tier option within the brand's extensive range of dive watches. How the Sumo nickname came about is the subject of a good amount of debate among enthusiasts, but the most common reason given, and the most straightforward, is the watch's extra-large diameter of 45mm. In the 12 years that have passed since the Sumo's inaugural bout, Seiko enthusiasts the world over have longed for an updated model. Sure, there were a number of color variations released over the years in classic dive watch standbys like orange and blue, but the overall design – from the case to the movement – remained unaltered.
That changed this year. At Baselworld 2019, the monolithic giant of Japanese watchmaking quietly discontinued the standard Sumo, while revealing two new models with a refreshed appearance and a brand new caliber. As the first significant update to the original watch (SBDC031), Seiko made sure the most important details carried over. These include a stainless steel case with a mixture of polishing and brushing, water resistance tested to 200 meters below sea level, hour markers and hands coated with a hearty application of Seiko's favored LumiBrite material, drilled lugs, and all the specs you'd expect out of an ISO-certified dive watch (unidirectional 60-minute bezel, screw-down crown, aluminum bezel insert, and a three-link, stainless steel bracelet that comes with a dive extension) are present and accounted for.
Despite its substantial diameter, anyone that has strapped a Sumo on will be able to tell you the watch wears much smaller than expected thanks to its relatively short lugs, which contour nicely to the wrist. Seiko went a step further in the wearability aspect by bumping the new Sumo down a few weight classes with a thickness of just 12.5mm. This was possible for a few reasons, chiefly due to the presence of the automatic 6R35 movement, a caliber that is making its debut here. The 6R35 replaces the previous 6R15 and boasts a 70-hour power reserve (over 20 hours more than its predecessor) and a beat rate of 3Hz. In addition to all that's happening inside the watch, Seiko streamlined the appearance of the dial as well, with slightly thinner hands and hour markers that occupy less of the overall dial real estate. And protecting the dial? A sapphire crystal, taking the place of Seiko's proprietary "Hardlex" (mineral-based) glass found on all previous Sumo entries.
There are two watches that make up the new-and-improved Sumo line, and we're adding both of them to the Shop today. The SPB101 has a non-reflective black dial, while the SPB103 has a green dial with a sunburst effect. The option for a green dial will be most relevant for completists, as this is the first time the brand has offered a Sumo in the color. Compared to the black dial, the green option is extremely reflective, appearing to shift between tones depending on the amount of light available. In direct sunlight, the green will be vibrant and dance with each reflection, while in low light conditions, the green darkens and assumes an almost black hue.
Long positioned in the middle ground for Seiko dive watches – between the cult-favorite "Turtle" series and the more premium MarineMaster – the new Sumo, priced at $850 in both of its colorways, maintains its station well, immediately becoming one of the highest grade dive watch options in the sub-$1,000 segment. While there is no questioning the performance value of these watches, they also have a defined sense of style that makes them suitable for everything from a business lunch in the city to a weekend vacation. See for yourself in the HODINKEE Shop now.