Seiko Prospex Sea 1968 Heritage Diver's GMT Limited EditionvsSynchron Poseidon
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Measurements
Catalog photos are all shot at the same flattering size. These aren't: every case below shares one millimeter scale.

Prospex Sea 1968 Heritage Diver's GMT Limited Edition

Poseidon
Diameter
42mm
41mm
Lug-to-Lug
48.6mm
45mm
lowest
Thickness
13.3mm
11.9mm
lowest
Water Resistance
300m
300m
Power Reserve
72h
highest
68h
MSRP
$1,750
n/a
Movement
Seiko 6R54
La Joux-Perret G100
Case
4 specsCrystal & Dial
3 specsMovement
3 specsPricing
1 specsReviews
Synthesized for each watch independently from owner discussions, enthusiast forums, written reviews, and video reviewers.
The Seiko Prospex Sea 1968 Heritage Diver's GMT Watch Limited Edition is widely praised for its excellent quality and finishing for its price, with reviewers highlighting its beautiful case, bracelet, and Lumibrite lume. Owners appreciate the comfortable 42mm case size and the 4 o'clock crown position. The watch features a sapphire crystal and uses the in-house 6R54 automatic movement with a three-day power reserve. Some reviewers note that the GMT function is secondary and that the bezel clicks are quieter than expected. The 4:30 date window splits opinion among enthusiasts, and it is described as a "caller GMT" rather than a true "traveller GMT." Overall, owners and reviewers rate the Seiko Prospex Sea 1968 Heritage Diver's GMT Watch Limited Edition highly for its excellent value, quality finishing, and comfortable wearability.
Owners widely praise the Synchron Poseidon for its vintage-inspired diver aesthetics, easy-to-read dial, and precise, grippy bezel. The La Joux-Perret G100 movement is consistently noted as a strong point, with owners reporting good timekeeping, one seeing accuracy around -4 seconds per day, and others highlighting its 68-hour power reserve. The winding action and crown operation are described as reassuring, with one reviewer stating it surpasses watches at double the price. Some find the design busy or the branding confusing, and the blasted finish on the steel bezel rim contrasts with the brushed case. One owner noted the included Isofrane strap can be long for smaller wrists. On balance, owners and reviewers rate the Synchron Poseidon highly for its robust build, reliable movement, and excellent value.
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