Seiko Adds a 39.4mm Field GMT Pair to the 5 Sports Line
Seiko has added a compact field GMT to 5 Sports. According to Revolution Watch, references HDB001K (green dial) and HDB002K (ivory dial) use a 39.4 mm steel case, a fixed 24-hour bezel and calibre 4R34. Australian retail was listed at AUD 675, with availability from August 2026.
The layout is a tool GMT rather than a dive GMT: three hour scales (12-hour dial, 24-hour dial ring, 24-hour bezel), an orange second-hour hand, drilled lugs and a five-link bracelet. Water resistance is 100 m, not the 200 m typical of Prospex divers.
Case and movement numbers
Published dimensions are 39.4 mm diameter, 47.9 mm lug to lug and 13.6 mm thickness, with the crown at 3 o’clock. Luminous markers and brushed steel dominate the finish. The five-link bracelet is closer to a dress-sports bracelet than a three-link diver. Readers comparing bracelet styles can use the Jubilee versus Oyster bracelet notes as a vocabulary check, even though Seiko does not use those Rolex names.
Calibre 4R34 is an automatic caller GMT: 3 Hz, 41-hour reserve, date, and a independently set 24-hour hand. Factory accuracy is quoted at −35 to +45 seconds per day in the Revolution spec block (the running text uses −34 to +45). The same calibre already powers 5 Sports Style GMT and Presage Cocktail Time GMT models. Aftermarket GMT discussion in the Seiko-mod community still centres on NH34, covered in the NH34 GMT aftermarket timeline; 4R34 is the jewelled, branded counterpart in complete watches.
| Reference | Dial | Case | Movement | Price / timing |
|---|---|---|---|---|
| HDB001K | Warm green | 39.4 × 47.9 × 13.6 mm, 100 m | 4R34, 41 h | AUD 675, from August 2026 |
| HDB002K | Ivory | Same | Same | Same |
How the two dials split the brief
HDB001K pairs a warm green field with orange GMT accents and the steel 24-hour bezel, a colour mix associated with field and travel watches. HDB002K uses ivory, which Revolution Watch described as closer to aged steel GMT dials, and more likely to be worn on leather than the green version. Both keep the orange GMT hand, so the complication colour is constant; only the main dial changes.
- Fixed steel 24-hour bezel (not a dive bezel)
- Drilled lugs for strap changes without a spring-bar tool at a bench
- Five-link bracelet as the stock metal option
- Caller GMT, not a true independent-hour traveller GMT
Place in the 2026 GMT stack
In the same year Seiko also issued Prospex 1968 Heritage Diver GMT pieces (HBC001/HBC002) with calibre 6R54, 300 m rating and a USD 1,700 tag, and a Presage Cocktail Time GMT in the 145th-anniversary Edo Purple series. The Field GMT sits below those on price and water resistance, and above older 5 Sports GMTs in case diameter control (under 40 mm).
Revolution Watch recorded Australian pricing only. Other-market SRP figures were not in that July 2026 article.
FAQ
Is the bezel rotatable?
No. It is a fixed 24-hour scale. Dual time is read from the GMT hand against the bezel and the inner 24-hour ring.
What is the difference between HDB001K and HDB002K?
Dial colour only in the published spec: green versus ivory. Case, movement, bracelet and water resistance are shared.
When did it go on sale?
According to Revolution Watch, from August 2026 at AUD 675.
Source: According to Revolution Watch (23 July 2026, Felix Scholz) and the published Seiko 5 Sports Field GMT specification table.