Side by side

Bremont Supermarine 300MvsSeiko Prospex Sea 1968 Heritage Diver's GMT

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

Supermarine 300M
BremontSupermarine 300M
MSRP $3,550
Prospex Sea 1968 Heritage Diver's GMT
SeikoProspex Sea 1968 Heritage Diver's GMT
MSRP $1,500

At a glance

12 of 29 specs differ
Diameter
Supermarine 300M40mm
Prospex Sea 1968 Heritage Diver's GMT42mm
Power Reserve
Supermarine 300M40h
Prospex Sea 1968 Heritage Diver's GMT72h
Water Resistance
Supermarine 300M300m
Prospex Sea 1968 Heritage Diver's GMT200m
MSRP
Supermarine 300M$3,550
Prospex Sea 1968 Heritage Diver's GMT$1,500

Full specifications

Case

5 specs
Diameter
40mm
42mm
Thickness
12mm
12.9mm
Lug-to-Lug
48.6mm
Material
904L Stainless Steel
Stainless Steel
Water Resistance
300m
200m

Crystal & Dial

3 specs
AR Coating
Inner
Anti-reflective coating on inner surface
Dial Color
Green
Black
Lume
None
LumiBrite on hands, index(es) and bezel

Movement

3 specs
Caliber
BE-92AE
6R54
Power Reserve
40h
72h
Jewels
25
24

Pricing

1 specs
MSRP
$3,550
$1,500

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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.

Bremont Supermarine 300M

The Bremont Supermarine 300M is praised for its comfortable 40mm and 42mm case sizes, with owners noting the 42mm wears well on smaller wrists due to its lug design. One owner highlights the 13mm thinness of the 40mm case, considered compact for a 300m diver. The watch is priced at $1375. On balance, owners and reviewers appreciate the Bremont Supermarine 300M for its wearability and compact dimensions, especially for a dive watch.

Seiko Prospex Sea 1968 Heritage Diver's GMT

The Seiko Prospex Sea 1968 Heritage Diver's GMT is widely praised for its build quality, finishing, and comfortable wearability, offering good value for its price point. Owners and reviewers highlight the attractive silver/white sunray dial, blue ceramic bezel, and the premium feel of the improved bracelet clasp with excellent micro-adjustment. The Caliber 6R54 movement provides a 72-hour power reserve, and real-world accuracy often exceeds its stated range of +25 to -15 seconds per day, with some owners reporting figures around +3 to +5 seconds per day. However, the caller-style GMT functionality is a point of contention for some, who find the GMT scale difficult to read and prefer a flyer GMT at this price. Some also find the crown position at 4 o'clock undesirable, and a few note a lack of dial contrast or illegibility of the inner bezel.

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