Omega Seamaster Planet Ocean 600M Co Axial Master Chronometer 39.5mmvsZenith Defy Revival A3643
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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.

Seamaster Planet Ocean 600M Co Axial Master Chronometer 39.5mm

Defy Revival A3643
Diameter
39.5mm
37mm
Lug-to-Lug
45.6mm
n/a
Thickness
14.2mm
n/a
Water Resistance
600m
highest
300m
Power Reserve
55h
highest
50h
MSRP
n/a
$7,800
Movement
Omega 8800
n/a
Case
6 specsCrystal & Dial
3 specsMovement
6 specsPricing
1 specsReviews
Synthesized for each watch independently from owner discussions, enthusiast forums, written reviews, and video reviewers.
The Omega Seamaster Planet Ocean 600M Co Axial Master Chronometer 39.5mm is praised for its excellent finishing and handsome, easy-to-read dial with good lume. Owners find the 39.5mm size suitable for smaller wrists, though some describe it as a chunky or heavy piece. The Co-Axial movement is noted for potentially increasing service intervals. Opinions are divided on the case proportions, with some finding them strange or awkward due to the 14.5mm thickness, while others appreciate its substantial build and comfortable bracelet with a useful micro-adjust clasp, though one reviewer noted a lack of micro-adjustment on the steel bracelet. The "Summer Blue" dial is considered pretty, and the watch retains its 600m water resistance and helium escape valve. One reviewer found a specific brown ceramic and gold combination visually jarring.
Owners widely praise the Zenith Defy Revival A3643 for its faithful 1969 reissue, featuring a crisp silver sunburst dial, sharp hands, and a sculptural 14-sided bezel within an eight-sided case. Its 37mm size and case geometry allow it to wear vintage without feeling top-heavy, and the 300m water resistance makes it a chic dive watch. The Gay Frères-inspired ladder bracelet, though divisive, offers comfortable wear with period correctness. One owner notes the lume is significantly brighter than on other Zenith models. Accuracy figures vary, with one owner reporting -5 seconds per day and another experiencing -10 to -15 seconds per day issues. The price is $7,800. Overall, owners rate the Zenith Defy Revival A3643 highly for its faithful reissue and comfortable wearability at the price.
The octagonal case and fourteen-sided bezel are consistently praised. The 15mm thickness is considered substantial for the 37mm case size.
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