Side by side

Bremont Supermarine 300MvsGrand Seiko SBGR321

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

Supermarine 300M
BremontSupermarine 300M
MSRP $3,550
SBGR321
Grand SeikoSBGR321
MSRP $5,200

At a glance

10 of 29 specs differ
Diameter
Supermarine 300M40mm
SBGR32140mm
Power Reserve
Supermarine 300M40h
SBGR32172h
Water Resistance
Supermarine 300M300m
SBGR321100m
MSRP
Supermarine 300M$3,550
SBGR321$5,200

Full specifications

Case

5 specs
Category
Diver
Dress
Thickness
12mm
13mm
Lug-to-Lug
46.6mm
Material
904L Stainless Steel
Stainless Steel
Water Resistance
300m
100m

Crystal & Dial

2 specs
AR Coating
Inner
Yes
Dial Color
Green
Black

Movement

2 specs
Caliber
BE-92AE
9S65
Power Reserve
40h
72h

Pricing

1 specs
MSRP
$3,550
$5,200

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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.

Grand Seiko SBGR321

Grand Seiko SBGR321 owners and reviewers widely praise its attractive design, compelling dimensions, and robust movement. The watch features sharp case lines with contrasting brushing and polishing, a 40mm steel case that provides presence without bulk, and 100m water resistance. Its sunburst blue dial, inspired by the dawn sky over Mount Iwate, showcases Grand Seiko's signature finishing on applied markers and hands, with a red-tipped seconds hand. The 9S65 automatic movement is noted for its precision, running within specifications, with one source reporting a +5 to -3 seconds a day rate and a 3-day power reserve. A blue rotor with a crimson rim, also inspired by Mount Iwate, is visible through the display caseback. On balance, owners and reviewers rate the Grand Seiko SBGR321 highly for its exceptional finishing and compelling blue dial design at its price point.

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