Seiko Cal. 5640 - 531

The Seiko 5640-531 represents an important milestone in Seiko's 1990 lineup. Powered by the 5640 caliber with 27j jewels beating at 28,800 bph, it delivers a 40 hours power reserve. [seikata-wm-f52071ec48a2]

Also known as: Helmet, Baby Tuna

Specifications

Movement

Spring Drive

Case Material

Two-Tone

Case Width

40mm

Case Thickness

10.6mm

Lug Width

18mm

Crystal

Acrylic

Bezel

Bidirectional

Water Resistance

70m

Dial Color

Cream

Jewels

27j

Frequency

28,800 bph

Power Reserve

40 hours

Year

1990

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