Seiko Cal. 5631 - 387

The Seiko 5631-387 represents an important milestone in Seiko's 1990 lineup. Powered by the 5631 caliber with 18j jewels beating at 28,800 bph, it delivers a 36 hours power reserve. [seikata-wm-c6a70a4bcafa]

Also known as: Tuna, Bullhead

Specifications

Movement

Spring Drive

Case Material

Gold-Plated

Case Width

43mm

Case Thickness

15.7mm

Lug Width

20mm

Crystal

Hardlex

Bezel

Inner Rotating

Water Resistance

150m

Dial Color

Navy

Jewels

18j

Frequency

28,800 bph

Power Reserve

36 hours

Year

1990

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