Seiko Cal. 4521 - 631

This Spring Drive model from 1977 features a 37mm PVD Black case. Powered by the 4521 caliber with 22j jewels beating at 28,800 bph, it delivers a 70 hours power reserve. [seikata-wm-eddd9c38c01e]

Also known as: Helmet

Specifications

Movement

Spring Drive

Case Material

PVD Black

Case Width

37mm

Case Thickness

10.3mm

Lug Width

20mm

Crystal

Sapphire

Bezel

Bidirectional

Water Resistance

50m

Dial Color

Green

Jewels

22j

Frequency

28,800 bph

Power Reserve

70 hours

Year

1977

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