Squale 1521 Classic COSCvsSeiko Prospex Sea

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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.

1521 Classic COSC

Prospex Sea
Diameter
42mm
43.8mm
Lug-to-Lug
48mm
lowest
48.7mm
Thickness
12.5mm
lowest
12.8mm
Water Resistance
500m
highest
200m
Power Reserve
38h
41h
highest
MSRP
$1,965
$625
lowest
Movement
Sellita SW200-1
Seiko 4R35
Case
6 specsCrystal & Dial
5 specsMovement
3 specsPricing
1 specsReviews
Synthesized for each watch independently from owner discussions, enthusiast forums, written reviews, and video reviewers.
Owners widely praise the Squale 1521 Classic COSC's well-proportioned 42mm case, with one reviewer calling it a masterclass in case design. The COSC certification is noted to improve accuracy, and the bezel indices are now fully lumed, a feature some owners find superior. The brushed case with polished chamfers is described as a significant and attractive aesthetic update. However, some owners prefer older bezel designs, and opinions on the lume are mixed, with one user finding it only "okay." One owner reported moisture ingress after a shower due to a loose case back on a new watch. The Squale 1521 Classic COSC is priced at CHF 1,475 and uses a Sellita SW200-1 movement. Overall, owners rate the Squale 1521 Classic COSC highly for its updated finishing and improved accuracy.
The Seiko Prospex Sea is widely praised for its excellent value as a sport watch, with owners highlighting its comfortable wearability and generous lume. Reviewers note its solid build quality and attractive design, with some specifically mentioning the matte black dial as a strong point. One owner reports accuracy around +1 to +2 seconds per day. The 43.8mm case size is considered substantial by some, and one owner found the watch heavy and thick, regretting not choosing a different variant. Overall, owners and reviewers rate the Seiko Prospex Sea highly for its blend of classic design and modern utility at an accessible price point.
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