Formex Reef 39.5 mmvsSeiko Prospex Sea 1965 Heritage Diver's Watch
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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.

Reef 39.5 mm

Prospex Sea 1965 Heritage Diver's Watch
Diameter
39.5mm
40mm
Lug-to-Lug
45.5mm
lowest
46.4mm
Thickness
11mm
lowest
13mm
Water Resistance
300m
300m
Power Reserve
56h
72h
highest
MSRP
$2,230
$1,300
lowest
Movement
Sellita SW300-1
Seiko 6R55
Case
4 specsCrystal & Dial
4 specsMovement
3 specsPricing
1 specsReviews
Synthesized for each watch independently from owner discussions, enthusiast forums, written reviews, and video reviewers.
The Formex Reef 39.5 mm is widely praised for its refined finishing, improved proportions, and compelling value under €2,000. Owners and reviewers highlight its comfortable wearability on smaller wrists, unique aesthetic, and impressive specifications including 300m water resistance and a COSC-certified Sellita SW300-1 movement. Some note the 22mm lug width feels slightly disproportionate and the bracelet could benefit from more taper. A prototype crown protrusion issue is expected to be resolved in production. Overall, owners rate the Formex Reef 39.5 mm highly for its excellent build quality and tool-like features at its price point.
Owners widely praise the Seiko Prospex Sea 1965 Heritage Diver's Watch for its refined engineering, comfortable 40mm case, and improved 300m water resistance. The watch is noted for its better build quality and finishing compared to some alternatives, featuring a mix of polished and brushed surfaces, with specific callouts for the jewel-toned teal dial with a rippling-water pattern. Some owners consider the price fair, while others suggest it is too high. Accuracy figures vary, with some owners reporting their 6R55 movement performs well within +/- 10 seconds per day, while others note theirs runs slow or have concerns about QC for the price. The bracelet, while improved, lacks modern features like quick-release or extensive micro-adjustments. Overall, owners and reviewers rate the Seiko Prospex Sea 1965 Heritage Diver's Watch highly for its refined design and build quality at its price point.
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