Seiko Cal. 5631 - 538

The Seiko 5631-538 represents an important milestone in Seiko's 1971 lineup. With its 20mm lug width and 8.7mm profile, it sits comfortably on most wrists. [seikata-wm-8bb9adeffed6]

Also known as: Tuna

Specifications

Movement

Kinetic

Case Material

Gold-Plated

Case Width

43mm

Case Thickness

8.7mm

Lug Width

20mm

Crystal

Hardlex

Bezel

Coin-Edge

Water Resistance

40m

Dial Color

Black

Jewels

30j

Frequency

21,600 bph

Power Reserve

42 hours

Year

1971

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