Hands-on with the Seiko Prospex Sumo Solar GMT Diver SFK001J1 & SFK003J1 Watches

There’s been a number of impressive Seiko Prospex launches recently and alongside the new 2023 Black Series ‘Night’ models, there is a pair of designs that have really caught our eye. The Seiko Prospex Sumo Solar GMT Diver watches under references SFK001J1 and SFK003J1 are the first solar-powered Seiko Prospex watches we’ve seen with a GMT hand, powered by their freshly debuted Calibre 5K62 housed within their bulky ‘Sumo’ case.

We all have different tastes when it comes to our “daily-beater” watches. Some of us lean more towards slender, smaller sized dress watches, while there are those of us that can’t say no to oversized sports watches like the Seiko Prospex Sumo Solar GMT Diver. This design is certainly what you’d call a ‘large watch’, with its nickname ‘the Sumo’ referencing its hefty 45mm diameter and 20mm band width. Alongside the portly case, the Seiko Sumo watch is also named as such for the marker at 12 o’clock which evokes ‘Mawashi’, the underwater worn by Japanese sumo wrestlers.

Trust us when we say the Seiko Prospex Sumo Solar GMT Diver watches are large watches; the 45mm diameter and 52mm lug-to-lug measurement will certainly not find a home on as many wrists as some of the other more compact Seiko Prospex watches. However with that being said, the Seiko Sumo watches of recent years have felt easier to wear with their twisted lugs and curved profile fitting effortlessly to the skin. The cases have alternating polished bevels and brushed lines and the iconic 4 o’clock screw in crown for a 200 metre water resistant rating. There’s also a screw down closed case back and scratch resistant sapphire crystal glass with anti-reflective treatment.

Adding two new colourways to its bezel, the new Seiko Prospex Sumo Solar GMT Diver watches now come in a choice of blue or green on the bezel insert. The bezel is still unidirectional for those that want to take their Prospex out diving, and is decorated with a white 60 minute scale and a Lumibrite marker up top. The designs pair their freshly coloured bezel with a dial to match; reference SFK001J1 elects a gorgeous nautical blue display while reference SFK003J1 nominates a deep forest green hue. Both dials are generously adorned in Lumibrite markers on the hands and indexes, including the well-known Sumo belt marker at 12 o’clock.

The dials of the Seiko Prospex Sumo Solar GMT Diver watches are subtly grained with an elegantly pressed pattern design. It’s a fine horizontal wave pattern which is relatively discreet but adds a nice playful touch to the otherwise conservative display. The dials are also joined by four central hands, two large sword-shaped hands for the hours and minutes, a lollipop seconds hand and a bright orange GMT hand which contrasts boldly to both the blue and green dials. There’s also a date window at 3 o’clock and a 24 hour scale beside the minutes track which outlines the day and night hours. The Seiko Prospex Sumo Solar GMT Diver SFK001J1 watch presents its 24 hour scale in opposing shades of blue while the Seiko Prospex Sumo Solar GMT Diver SFK003J1 watch presents the day hours in a muted lime green and the night hours in a darker green shade.

Powering the new Seiko Prospex Sumo Solar GMT Diver watches is the brand-new Calibre 5K56 movement which offers solar-quartz technology. This means the battery will never need replacing as it becomes naturally fuelled by natural or artificial light. The in-house movement also guarantees a maximum power reserve of nine months and accuracy of +/- 15 seconds a month. The GMT function is manipulated by the 4 o’clock crown and the movement of the date is tied to the local hour hand so you can correct the date in either direction if needed. The Seiko Prospex Sumo Solar GMT Diver watches are completed by traditional three-row link bracelets in stainless steel which secure by a three-fold clasp. The clasps are complete with a secure lock and push button release with extender.

If you’d like to learn more about the new Seiko Prospex Sumo Solar GMT Diver watches and secure one of the designs for yourself, head over to the Jura Watches website here. Alternatively, get in touch with the team by calling 01335 453453 or send us a message at help@jurawatches.co.uk.


  • Case Size: 45mm
  • Case Material: Stainless steel
  • Bezel: Unidirectional with 60 minute divers scale, Lumibrite markers, green or blue insert
  • Glass: Sapphire crystal with anti-reflective treatment
  • Crown: Screw in
  • Case Back: Closed, screw down
  • Water Resistance: 200 metres
  • Movement: Calibre 5K65, solar-powered quartz
  • Functions: Hours, minutes, seconds, date, GMT
  • Accuracy: +/- 15 seconds a month
  • Dial: Green or blue with Lumibrite markers and hands, 24 hour scale with two-toned markings for day and night hours
  • Strap: Three-row link stainless steel bracelet
  • Buckle: Three-fold clasp with secure lock and push button release with extender
  • Limited: No
  • References: SFK001J1 (Blue) and SFK003J1 (Green)
  • RRP: £660