Seiko Prospex Sumo SPB103J1 Review: Features and Performance of the Timepiece

The Seiko Prospex "Sumo" SPB103j1 has a sleek and modern design that is both stylish and functional.

Marianna du Maurier
6 Min Read

We are excited to share our review and complete guide of the Seiko Prospex ”Sumo” SPB103j1. This watch is popular among watch enthusiasts due to its durability, reliability, and overall quality.

In this article, we will provide an in-depth review of the Seiko Prospex ”Sumo” SPB103j1. We will cover its design, features, and movement, as well as its pros and cons, and give you our overall opinion on this watch.

Seiko Prospex “Sumo” SPB103j1 Review & Complete Guide

Seiko is a well-known brand that produces high-quality watches that are both affordable and durable. The Seiko Prospex “Sumo” SPB103j1 is no exception. This watch is designed for those who need a reliable and sturdy timepiece for their active lifestyle.


The Seiko Prospex “Sumo” SPB103j1 has a sleek and modern design that is both stylish and functional. The watch features a unidirectional rotating bezel for measuring elapsed time, which is essential for any dive watch.

The bezel is quite wide and has a bold green aluminum insert that adds a pop of color to the watch.


The Seiko Prospex “Sumo” SPB103j1 is built to last. Its water resistance is 200m/660 feet, making it suitable for swimming, diving, and essentially any type of water activity.

The watch is constructed with a durable stainless steel case and bracelet that can withstand the wear and tear of an active lifestyle.


The Seiko Prospex “Sumo” SPB103j1 is powered by a reliable automatic movement that is hidden underneath a screwed steel case back. The movement is accurate and requires no battery changes, making it a low-maintenance timepiece.


The Seiko Prospex “Sumo” SPB103j1 is priced at around EUR 850, a reasonable price for a watch of this quality and durability. While it may be more expensive than some of Seiko’s other watches, it is still a great value for money, considering the features and design.

Seiko Prospex ”Sumo” SPB103j1 Review

Seiko Prospex ”Sumo” SPB103j1 Case

The Seiko Prospex ”Sumo” SPB103j1 features the iconic ”Sumo” case, known for its large, sturdy, and robust design. The stainless steel case has a diameter of 45mm, a thickness of 13.5mm, and a lug-to-lug measurement of 52.5mm, providing a substantial presence on the wrist.

The case is well-finished, with satin-brushed lugs and polished sides. The absence of crown guards allows for a more streamlined look, while the recessed screw-down crown at the 4 o’clock position ensures protection and comfort.

With a water resistance of 200m/660 feet, the SPB103j1 is suitable for various water activities. Additionally, it features a unidirectional rotating bezel with a bold green aluminum insert, offering optimal legibility and enhanced protection due to its sloped edge. The watch is equipped with a sapphire crystal and a solid steel screw-down case back with the iconic Seiko tsunami emblem.

Seiko Prospex ”Sumo” SPB103j1 Dial

The dial of the SPB103j1 is a striking, vibrant green with a sunburst brushed finish, providing a captivating play of light and color. The large hour markers and hands offer excellent contrast against the dial, ensuring exceptional legibility.

The applied hour markers with polished metal frames applied Lumibrite, and the sword-shaped minute and hour hands contribute to the watch’s bold and functional aesthetic. The watch also features a large date window at 3 o’clock and an angled chapter ring, adding depth and visual interest to the dial.


The SPB103j1 is powered by the in-house Seiko caliber 6R35, an automatic movement with a frequency of 21600 BPH (3Hz), 24 jewels, and a power reserve of 70 hours.

This movement displays minutes, seconds, hours, and the date, with a quick-set function for easy adjustment. The 6R35 movement represents an upgrade from the previous 6R15, offering improved power reserve and refined functionality.


This timepiece comes with a three-link satin-brushed bracelet featuring polished edges on the middle links, as well as a diver’s extension and safety clasp.

The 20mm bracelet complements the watch’s sporty design and is beautifully finished. It offers a solid and comfortable fit. The drilled lugs allow for easy bracelet changes, providing versatility for personalization.


  • Movement: Seiko in-house caliber 6R35
  • Water Resistance: 200m/660 feet
  • Case Diameter: 45mm
  • Case Thickness: 13.5mm
  • Lug-to-Lug Measurement: 52.5mm
  • Crystal: Sapphire
  • Power Reserve: 70 hours

This comprehensive review provides insight into the design, functionality, and features of the Seiko Prospex ”Sumo” SPB103j1. It showcases its capabilities as a professional dive watch with a distinct and enduring aesthetic.

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