Seiko Introduces Its First Mechanical Prospex Diver’s Watch With GMT Function

The new collection features Seiko’s first use of a mechanical GMT movement in a Prospex diver’s watch.

As surprising as it may sound, after more than half a century of Seiko Prospex dive watches (the first dating back to 1965), there has never been a single model with a GMT mechanical movement…until today, with the new line of watches. There have been dozens of mechanical dive watches, but the overall concept of a mechanical GMT x Dive watch remains the exclusiveness of the easy-to-use Seiko 5 Movement range for now – and we’re reviewing a very cool trio here. It’s time for something more technical and resilient with the new Prospex 1968 Diver’s Modern Re-interpretation GMT SPB381, SPB383 and SPB385.

The association of the GMT function with the functionality of a diver’s watch has long been one of our favorite types of watches. All in all, this combination of features is a great summer watch for diving and travel. Looking at Seiko’s portfolio, very few models feature this combination. The only explanation I can find for a Prospex Diver watch with a GMT complication is that it is part of the high-end LX line and is powered by a Spring Drive movement – more details here and here. Today, cheap Seiko fills a void in its ever-growing Prospex collection with the launch of the first GMT mechanical diver’s watch with a new movement.

The design of this new series of watches is very familiar and is based on the brand’s iconic diving watch from 1968, reference 6159-7001. First reissued in a high-end high-frequency watch – the SLA025 – the vintage watch’s angular and robust look has since appeared in more regular collections for all occasions. The latest iterations of these modern reinterpreted models of the Prospex 1968 Diver are the SLA055 and SLA057, again belonging to the premium part of the brand’s portfolio. The closest models to the current GMT series are the relatively new SPB185 and SPB187, which share the same proportions and are in the same price segment. However, Seiko has profoundly reinvented this concept, making the new GMT Divers watches unique.

In terms of design, the connection to the original 1968 watch is evident. Strong shoulders, angular shapes, crown at 4 o’clock, wide bezel, strong lines around the case and alternating polished accents and hairline finishes. According to the brand, the case has been redesigned with shorter lugs and improved ergonomics for improved wrist comfort. Visually, these new models, SPB381, SPB383 and SPB385, are clearly dive-oriented models with a 60-minute scale on the ceramic insert. They feature screw-down crowns and casebacks, are made of steel with a super-hard coating, have domed sapphire crystals, and are water-resistant to 200 meters. The case measures 42mm in diameter and 12.9mm in height—not thin, but still acceptable.

Nor does the dial give away its connection to the 1968 model. The large hour-markers and hands are filled with LumiBrite and have the same design as the vintage model. New is the integration of the central 24-hour GMT hand and the 24-hour scale on the inner flange – a solution that, while not offering the best legibility, preserves the 60-minute diving scale. It is important to note that these SPB381, SPB383 and SPB385 are office GMT watches as it has an independently adjustable GMT hand.

Inside the case is the new self-winding caliber 6R54, which, like all 6Rxx series calibers, benefits from a comfortable power reserve. It beats at a frequency of 3 Hz and can store energy for up to 72 hours when fully wound. It displays the date in addition to time and GMT. All three watches are equipped with a newly designed ultra-hard coated stainless steel bracelet with folding clasp and diving watch extension.

Seiko is releasing three versions of its first mechanical GMT diver’s watch. First up are two watches that will become permanent collections: the SPB381 with a green dial and green ceramic bezel, and the SPB383 with a black dial and black ceramic bezel. Both have yellow GMT online shop

In addition, Seiko has released a new Save the Ocean limited edition model SPB385. Helping to better understand the world’s oceans and their conservation, this model features a rather cool textured ice blue dial inspired by the polar glaciers that shape Arctic and Antarctic landscapes and seascapes – a theme we’ve seen in previous Rescue Marine versions here and here. It has a black ceramic bezel and dark blue GMT hands. It is paired with the same stainless steel bracelet as the above model, and it also comes with a strap made from recycled plastic bottles using a traditional Japanese weaving technique called Seichu.

Case: 42mm diameter x 12.9mm height – stainless steel case, superhard coating, brushed finish with polished accents – unidirectional bezel, black or green ceramic insert, engraved 60-minute scale and luminous pearl – with anti-reflective Coated Domed Sapphire Crystal – Screw-Down Solid Steel Case Back – Screw-Down Crown – 200M Water Resistance
Dial: All models with large markers and hands, filled with LumiBrite – date at 4:30
SPB381 – Green Dial, Matte Finish, Yellow GMT Hand, Green 24 Hour Inner Flange
SPB383 – Black Dial, Matte Finish, Yellow GMT Hand, Black 24 Hour Inner Flange
SPB385 Save the Ocean – Ice blue polar texture, dark blue GMT pointer, ice blue 24-hour flange
Movement: Caliber 6R54 – Manufacture – Automatic – 24 jewels – 27.4mm x 5.3mm – 21,600 vibrations/hour – 72 hours power reserve – Hours, minutes, seconds, independent (office-like) 24-hour GMT hand, date
Bracelet: Stainless Steel Bracelet with Super Hard Coating – Tri-Fold Clasp with Push Buttons, Safety Lock and Dive Extension – Save the Ocean SPB385 Comes with additional recycled polyester strap
Reference: SPB381-Green
SPB385 – Save the Ocean Ice Blue