The Seiko Prospex Sumo SPB103J1 is part of Seiko's extensive and legendary diving watch collection, and has received the heavyweight nickname of 'Sumo'. Another nickname that was, perhaps more kindly, bestowed upon it was 'MM200', which is short for MarineMaster 200 (200 for the water resistance, as the Marinemaster itself is 300m water resistant). The Marinemaster is Seiko's their high-end, no limits, diving watch that has garnered an incredible amount of praise over the years for being one of the best diving watches out there. That does set the bar pretty high for a watch at around 1/4th the price.

Is this watch as good as a 'real' Marinemaster? No, but it does punch above it's weightclass, regardless of being a 'Sumo. To start, it's a healthy 45mm in diameter, with a lug to lug distance of 52.6mm. That does mean it has a fairly substantial wrist presence, which is generally agreeable for a serious diving watch. 200m water resistance, a sapphire crystal and a high level of finishing are all part of the boxes that you can check on your 'diving watch wishlist'. What shouldn't be forgotten especially is the engine that powers this beast; the Seiko in-house Cal. 6R35 mechanical, automatic, movement, which features an impressive 70 hour power reserve. Definitely a drivetrain you can rely on.

The Sumo features great lume and a very legible, utilitarian design that is ideal when diving and for every day practicality. There is little chance you won't know what time it is! 

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• About Seiko

• *Authorised dealer of Seiko watches
  *100% brand new and unworn
  *Complete with the beautiful box and stamped warranty booklet
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  *Tens of thousands of satisfied customers

• We're an authorised dealer of all of our brands, unless otherwise noted. In this day and age there are also many 'grey market dealers' that compromise. What are the main benefits of buying from an authorised dealer with regard to the warranty?

  2 year warranty

  We offer a 2 year warranty on all watches. This covers all mechanical malfunction arising from parts failure and/or assembly errors. Excluded are parts that by their nature may not last 2 years, like batteries and leather straps, damage/problems caused by improper use and wear and tear. We stand behind the brands that we sell and the quality that they offer.
  Some of our brands also offer an international warranty, which will also apply.

  Service and parts

  In the unfortunate event of a problem with your watch, you simply need to send it to us (or take it to another dealer if the brand offers an international warranty). We have access to the official service centers, where only original parts are used and the watchmakers are qualified and experienced with your type of watch. Not every watch movement is the same, so it's best if it's handled by people who know what they are doing.
  After your 2 years warranty has expired we are able to offer service in most cases.

• Read all about Seiko on our dedicated brand page.