Seiko Prospex Marinemaster 1968 Heritage Diver's WatchvsSynchron Poseidon

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Measurements

Catalog photos are all shot at the same flattering size. These aren't: every case below shares one millimeter scale.

Seiko Prospex Marinemaster 1968 Heritage Diver's Watch at true scale

Prospex Marinemaster 1968 Heritage Diver's Watch

Synchron Poseidon at true scale

Poseidon

Diameter

42.6mm

41mm

Lug-to-Lug

49.3mm

45mm

lowest

Thickness

14.1mm

11.9mm

lowest

Water Resistance

300m

300m

Power Reserve

72h

highest

68h

MSRP

$3,600

n/a

Movement

Seiko 8L45

La Joux-Perret G100

Case

4 specs
Diameter
42.6mm
41mm
Thickness
14.1mm
11.9mm
Lug-to-Lug
49.3mm
45mm
Material
Stainless Steel
Titanium

Crystal & Dial

4 specs
Crystal Shape
Curved
n/a
AR Coating
Anti-reflective coating on inner surface
n/a
Dial Color
n/a
Sunshine Yellow
Lume
LumiBrite on hands, index(es) and bezel
None

Movement

3 specs
Caliber
Seiko 8L45
La Joux-Perret G100
Power Reserve
72h
68h
Jewels
35
0

Pricing

1 specs
MSRP
$3,600
n/a
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Reviews

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

Seiko Prospex Marinemaster 1968 Heritage Diver's Watch

Owners and reviewers widely praise the Seiko Prospex Marinemaster Marinemaster 1968 Heritage Diver's Watch for its exceptional finishing, comparable to Grand Seiko, and refined design, with particular appreciation for its case shape and the 4:00 crown position. The watch is noted for its enjoyable look and feel, and some consider it a significant step up from standard Prospex models, offering premium finishing and a tool-like appearance. The movement Seiko 8L45 is mentioned, along with a 72-hour power reserve and an accuracy of -5/+10 seconds per day. However, some find the price point high, and one reviewer noted the unsigned winding crown as a missed opportunity for a watch in this price range. On balance, owners and reviewers rate the Seiko Prospex Marinemaster Marinemaster 1968 Heritage Diver's Watch highly for its exceptional finishing and refined design at its price point.

Synchron Poseidon

Owners widely praise the Synchron Poseidon for its vintage-inspired diver aesthetics, easy-to-read dial, and precise, grippy bezel. The La Joux-Perret G100 movement is consistently noted as a strong point, with owners reporting good timekeeping, one seeing accuracy around -4 seconds per day, and others highlighting its 68-hour power reserve. The winding action and crown operation are described as reassuring, with one reviewer stating it surpasses watches at double the price. Some find the design busy or the branding confusing, and the blasted finish on the steel bezel rim contrasts with the brushed case. One owner noted the included Isofrane strap can be long for smaller wrists. On balance, owners and reviewers rate the Synchron Poseidon highly for its robust build, reliable movement, and excellent value.