Seiko Cal. 6638 - 691

The Seiko 6638-691 represents an important milestone in Seiko's 1991 lineup. It features a Navy dial protected by a Sapphire crystal and offers 140m of water resistance. [seikata-wm-d935be568a84]

Also known as: Helmet, Sportsmatic

Specifications

Movement

Kinetic

Case Material

Gold-Plated

Case Width

37mm

Case Thickness

14.4mm

Lug Width

18mm

Crystal

Sapphire

Bezel

Bidirectional

Water Resistance

140m

Dial Color

Navy

Jewels

25j

Frequency

36,000 bph

Power Reserve

41 hours

Year

1991

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