Side by side

Serica Ref. 5303 Diving ChronometervsFormex Reef 39.5 mm

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

Ref. 5303 Diving Chronometer
SericaRef. 5303 Diving Chronometer
MSRP $1,768
Reef 39.5 mm
FormexReef 39.5 mm
MSRP $2,230

At a glance

10 of 29 specs differ
Diameter
Ref. 5303 Diving Chronometer39mm
Reef 39.5 mm39.5mm
Power Reserve
Ref. 5303 Diving Chronometer42h
Reef 39.5 mm56h
Water Resistance
Ref. 5303 Diving Chronometer300m
Reef 39.5 mm300m
MSRP
Ref. 5303 Diving Chronometer$1,768
Reef 39.5 mm$2,230

Full specifications

Case

4 specs
Diameter
39mm
39.5mm
Thickness
12.2mm
11mm
Lug-to-Lug
46.5mm
45.5mm
Lug Width
20mm
22mm

Crystal & Dial

2 specs
AR Coating
Yes
Inner
Dial Color
Enamel Black
Bahama Blue

Movement

3 specs
Caliber
M100 COSC
Sellita SW300-1
Power Reserve
42h
56h
Complications
COSC
None

Pricing

1 specs
MSRP
$1,768
$2,230

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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.

Serica Ref. 5303 Diving Chronometer

Owners widely praise the Serica Ref. 5303 Diving Chronometer for its excellent wearability, definitive style, and smooth, confident bezel action. The dual scale on the bezel is noted as surprisingly useful, and the crown action, winding, and hacking are reported to work perfectly. One owner describes the Serica 5303-3 as gorgeous and unique, though another notes the crown can appear comically large. On balance, owners rate the Serica Ref. 5303 Diving Chronometer highly for its blend of unique design and robust functionality.

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.

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