Seamatic 300 GMT RGB10005/04 Rotary's travel diver goes jubilee

What is new about the Seamatic 300 GMT RGB10005/04?

Rotary introduced the Seamatic GMT in its autumn and winter 2024 collection, calling it the first GMT complication in the Seamatic range. Those first versions, such as the GS04378/96, came on a black dial and a silicone strap at an RRP of £299. The RGB10005/04 is the next step. Rotary's product record for it dates from August 2025, and it reached the brand's UK shop in September 2025.

Three things change. The dial is now deep blue. The bezel insert is a softer two-tone blue rather than the bold black and blue of the earlier model. And the silicone strap gives way to a polished stainless steel jubilee bracelet, the five-link style most people associate with travel watches. Rotary prices it at £349, so the bracelet and the new colours cost £50 over the strap version.

Since then Rotary has added more colours on the same bracelet, including a green dial (RGB10005/24) and a black edition, so this blue model is the first of a small family rather than a one-off.

How big is it, and how will it wear?

Rotary's specification table lists a 42 mm case with a height of 14 mm, while its product description quotes 42.5 mm and 13.8 mm. Either way, this is a full-size dive watch. The lug width is 22 mm, which makes aftermarket straps easy to find.

Rotary does not publish a lug-to-lug figure for the GMT. Watch Report measured the original three-hand Seamatic, which shares the general case design, at about 48 mm lug to lug. If that holds for the GMT, it will sit comfortably on wrists of roughly 17 cm and up. Smaller wrists may find the bezel and the jubilee bracelet a lot of steel. The polished centre links also make it a little flashier than a plain three-link bracelet would be.

What movement does it use, and how accurate is it?

Rotary only says it uses a Japanese automatic GMT movement. It does not name the calibre, and it does not publish accuracy or power reserve figures. A UK retailer listing for the Seamatic GMT, shared on hotukdeals, names the Seiko NH34 and quotes a 40-hour power reserve. That is a credible fit for a watch at this price, but it is a retailer's claim rather than Rotary's.

If it is the NH34, the 24-hour hand is set on its own from the crown. That suits keeping home time on the GMT hand while you reset the main hands for local time. Either way, expect a mechanical watch that needs the odd correction rather than quartz precision.

How well is it built?

The specification is strong for £349. Rotary lists a 316L stainless steel case, sapphire crystal and 300 m water resistance, which matches the rest of the Seamatic range. The bezel is a bi-directional 24-hour type, so with the GMT hand you can track a third time zone, as Rotary points out. Note that this means it is not a true dive bezel for timing a dive.

The date sits at three o'clock without a magnifier. The caseback carries Rotary's 130th anniversary engraving. Watch Report found the bracelet on the earlier three-hand Seamatic solid, with a flip-lock dive clasp and micro-adjust holes, and rated the lume as adequate rather than bright. Rotary also offers a two-year warranty with a third year added through its own site.

Is it good value against its rivals?

At an RRP of £349 it undercuts the two obvious Japanese alternatives. The Seiko 5 Sports Field GMT SSK059 has an RRP of £410 at Seiko UK. It is smaller at 39.4 mm, with a named Seiko movement, but only 100 m of water resistance and a Hardlex crystal. The Orient Mako GMT costs £499.99 in its regular colours, with an in-house Orient movement and 200 m water resistance.

Against those, the Rotary offers sapphire, 300 m and a full bracelet for less money. What you give up is brand detail: Seiko and Orient tell you exactly what is inside and how it should perform, while Rotary keeps that vague. Rotary's own GS04378/96 on silicone at £299 is also worth a look if you would rather have a strap.

What is the catch?

The main catch is the missing detail. With no named calibre, no accuracy figure and no power reserve from the brand, you are partly buying on trust. Rotary's two sets of case figures do not quite agree either.

Size is the second point. At 42 mm with a 14 mm height and a bracelet that tends to look busy, it is a lot of watch for a smaller wrist. Finally, it is too new for much owner feedback. The notes below come from the earlier three-hand Seamatic, which shares the case style but not the GMT movement.

“Sapphire, 300 m and a GMT hand for £349, as long as you can live without knowing exactly what is inside.”

What do owners say?

Themes from public owner feedback, paraphrased. We never copy Amazon reviews or ratings.

• Owners of the earlier three-hand Seamatic note later versions dropped the date magnifier and the Henley name, which they think improves the dial.

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