Side by side

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

The numbers, the dial colors, the calibers — laid out so you can stop flipping between tabs.

Reef 39.5 mm
FormexReef 39.5 mm
MSRP $2,230

At a glance

12 of 29 specs differ
Diameter
Reef 39.5 mm39.5mm
Prospex Sea 1965 Heritage Diver's Watch40mm
Power Reserve
Reef 39.5 mm56h
Prospex Sea 1965 Heritage Diver's Watch72h
Water Resistance
Reef 39.5 mm300m
Prospex Sea 1965 Heritage Diver's Watch300m
MSRP
Reef 39.5 mm$2,230
Prospex Sea 1965 Heritage Diver's Watch$1,300

Full specifications

Case

4 specs
Diameter
39.5mm
40mm
Thickness
11mm
13mm
Lug-to-Lug
45.5mm
46.4mm
Lug Width
22mm
20mm

Crystal & Dial

4 specs
Crystal Shape
Flat
Curved
AR Coating
Inner
Anti-reflective coating on inner surface
Dial Color
Bahama Blue
Black
Lume
Super-LumiNova
LumiBrite on hands, index(es) and bezel

Movement

3 specs
Caliber
Sellita SW300-1
6R55
Power Reserve
56h
72h
Jewels
25
24

Pricing

1 specs
MSRP
$2,230
$1,300

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What people say

Owners + reviewers, side by side

Synthesized for each watch independently from owner discussions, enthusiast forums, written reviews, and video reviewers.

Formex Reef 39.5 mm

The Formex Reef 39.5 mm is widely praised for its refined finishing, comfortable and well-proportioned case design, and impressive specifications for its price point, including COSC-certified Sellita SW300-1 movement and 300m water resistance. Owners and reviewers highlight the tool-less micro-adjust clasp and quick-release spring bars as practical features. Some reviewers note that the 22mm lug width feels slightly disproportionate to the smaller case, and the bracelet could benefit from more taper, though this is a point of contention for some owners who value the overall package. A prototype crown protrusion issue is noted as being addressed for production. On balance, owners and reviewers rate the Formex Reef 39.5 mm highly for its excellent value and well-executed design.

Seiko Prospex Sea 1965 Heritage Diver's Watch

The Seiko Prospex Sea 1965 Heritage Diver's Watch is praised for its refined engineering and updated features, including a 300m water resistance and a 72-hour power reserve from the Caliber 6R55 movement in a 40mm case. Owners note its better build quality and interesting finishing with a mix of polished and brushed surfaces. The "Tranquil Teal" variant features a jewel-toned dial with a rippling-water pattern. However, some owners consider the price too high, and concerns exist regarding the accuracy of the 6R movements, with some reporting theirs run slow. One review notes a reflective dial that impacts legibility. On balance, owners and reviewers appreciate the Seiko Prospex Sea 1965 Heritage Diver's Watch for its refined design and improved specifications over previous generations, despite some reservations about movement accuracy and price.

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