Seiko Prospex SPB381J1 Marine Green 1968 Heritage GMT Diver
Need a 42 mm Seiko diver that also shows a second time zone? The SPB381J1 is the Marine Green 1968 Heritage GMT. It keeps the cushion case and minute-marked dive bezel of the 1968 diver, and adds Caliber 6R54: a gold 24-hour hand, about 72 hours of reserve, and a date between 4 and 5.
This is regular production, not a numbered limited edition. The green dial, green ceramic bezel insert, and gold GMT hand are the Marine Green set. Black and ice-blue references exist in the same family. If the listing you want says SPB381J1, this is the green one.
How the GMT works on a dive bezel
The bezel is a unidirectional diver’s bezel, marked in minutes, with a green ceramic insert. It is not a 24-hour GMT bezel. You time a dive, or a parking meter, on that insert. The second time zone is the gold hand, read against the 24-hour numerals on the inner ring.
Caliber 6R54 is an office-style GMT. The 24-hour hand can be moved on its own in one-hour steps. The hour and minute hands stay on local time while you do that. It is not the traveller layout where the local hour hand jumps and the GMT hand stays fixed. Useful for a city you call often. Less useful if you want to reset home time in one click after a flight.
The dial reads GMT, Automatic 3 Days, and Diver’s 200m, and it is marked Japan. Hands, indexes, and the bezel pip carry LumiBrite. The crown sits at 4 and screws down. The case back is solid, engraved 6R54-00D0, sapphire crystal, and Diver’s Watch 200m, and it is marked Japan. A catalogue case-back photo can show a sample engraving. That number is not the serial of the watch we send.
Size, crystal, and what it is not
Seiko lists 42.0 mm diameter, 12.9 mm thickness, 48.6 mm lug-to-lug, and 20 mm between the lugs. Weight is 176 g. That is easier on the wrist than a 45 mm Sumo, and thicker than a dress Presage. The crystal is sapphire with anti-reflective coating on the inner surface, not Hardlex.
Water resistance is 200 metres, diver’s, with a screw case back. Recreational diving is inside that rating if the crown is screwed down and you follow normal care. It is not a Seiko 5 Sports GMT. Those use a different movement and a different case. It is also not a 1,000-piece limited edition, so you are buying a watch to wear, not a serial-number chase.
The bracelet is steel, with a three-fold clasp, a secure lock, a push-button release, and a diver’s extension. Chronospride inspects the stock before dispatch.
- Reference: SPB381J1 (SPB381)
- Movement: Seiko 6R54 automatic GMT, 24 jewels, manual wind, hacking, about 72 hours
- Accuracy: +25 to −15 seconds per day (Seiko specification)
- GMT: independently set 24-hour hand; local hour hand does not jump; dive bezel is a minute scale
- Case: stainless steel, 42.0 mm, 12.9 mm thick, 48.6 mm lug-to-lug, 20 mm lugs, about 176 g
- Crystal: sapphire, anti-reflective coating on the inner surface
- Bezel: unidirectional, green ceramic insert, minute scale
- Dial: marine green, gold GMT hand, date between 4 and 5, marked Japan
- Water resistance: 200 metres, diver’s; screw-down crown; solid screw case back
- Bracelet: steel, three-fold clasp with secure lock and extender
- Lume: LumiBrite on hands, indexes, and bezel
- Magnetic resistance: 4,800 A/m
- Edition: regular production, not a numbered limited edition
Frequently asked questions
Does the SPB381J1 have a GMT?
Yes, as an office-style GMT. Caliber 6R54 drives a gold 24-hour hand that you set on its own, in one-hour steps, without stopping local time. You read that hand against the 24-hour track on the inner ring. The hour hand is not the independently jumping hand used on a traveller GMT.
Is the bezel a GMT bezel or a dive bezel?
A dive bezel. It is unidirectional and marked in minutes, with a green ceramic insert. It does not rotate a second time zone. Use it as a dive timer. Use the gold hand for the other city.
What size is the SPB381J1?
42.0 mm diameter, 12.9 mm thick, 48.6 mm lug-to-lug, 20 mm lug width, about 176 g on the steel bracelet. Smaller than a Sumo. Larger than a 38 mm Seiko 5.
What movement does the SPB381J1 use?
Seiko Caliber 6R54. Automatic, hand-winding, hacking, 24 jewels, date between 4 and 5, about 72 hours of reserve. Seiko rates accuracy at +25 to −15 seconds per day. The case back is solid, so you will not see the movement through glass.
Is the SPB381J1 a limited edition?
No. The Marine Green 1968 Heritage GMT is regular production. Do not expect a piece number such as 0001 of 1000. If a catalogue photo shows an engraved sample number on the case back, that is not the serial of the unit we send.
Is 200 metres enough for diving?
Seiko rates it as a 200 m diver’s watch with a screw-down crown and a screw case back. Recreational diving is within that rating when the crown is down. It is not a saturation tool watch, and it is not a dress 50 m Presage.
Where can I buy the SPB381J1 in Australia?
Chronospride lists authentic stock of this Marine Green GMT, inspected before dispatch, with free Australia-wide shipping on eligible orders. The wider Seiko Prospex range is the place to compare other divers if 42 mm or a GMT is not what you need.
Buying this watch in Australia
Authentic stock, inspected before dispatch. Free shipping Australia-wide on eligible orders. Covered by Chronospride’s 12 months warranty, handled by our team. See our authenticity and warranty page. Match the 42 mm case and 20 mm lugs to a strap using the figures above, not a guess from the photo.
| Brand | Seiko |
|---|---|
| Case-Size | 42mm |
| Band-Width | 20mm |
| Lug-Width | 20mm |
| Lug to lug size | 48.6mm |
| Case Thickness | 12.9mm |