Side by side

Serica Ref. 5303 Diving ChronometervsSeiko Prospex Sea

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
Prospex Sea
SeikoProspex Sea
MSRP $1,100

At a glance

11 of 29 specs differ
Diameter
Ref. 5303 Diving Chronometer39mm
Prospex Sea41.3mm
Power Reserve
Ref. 5303 Diving Chronometer42h
Prospex Sea72h
Water Resistance
Ref. 5303 Diving Chronometer300m
Prospex Sea300m
MSRP
Ref. 5303 Diving Chronometer$1,768
Prospex Sea$1,100

Full specifications

Case

3 specs
Diameter
39mm
41.3mm
Thickness
12.2mm
12.5mm
Lug-to-Lug
46.5mm
48.2mm

Crystal & Dial

3 specs
AR Coating
Yes
Anti-reflective coating on inner surface
Dial Color
Enamel Black
Black
Lume
Super-LumiNova
LumiBrite on hands, index(es) and bezel

Movement

4 specs
Caliber
M100 COSC
6R55
Power Reserve
42h
72h
Jewels
25
24
Complications
COSC
None

Pricing

1 specs
MSRP
$1,768
$1,100

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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.

Seiko Prospex Sea

Seiko Prospex Sea models are widely praised for their excellent build quality, value for money, and comfortable wearability, with many appreciating the vintage-inspired designs and robust construction. Owners note the silicone straps are surprisingly comfortable and well-finished, and the Lumibrite lume is excellent. However, some find the 44.3mm size and thickness too large for smaller wrists, though others report the sizing as perfect. The 6R15 movement in some variants offers accuracy around +4 seconds per day with a 50-hour power reserve, while newer movements offer more. Some models are criticized for a bracelet width not matching the case size or a rudimentary clasp for their price point. Overall, owners and reviewers rate the Seiko Prospex Sea highly for its impressive case work and finishing at its price point.

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