Seiko Cal. 6639 - 366

The Seiko 6639-366 represents an important milestone in Seiko's 1981 lineup. With its 20mm lug width and 15.1mm profile, it sits comfortably on most wrists. [seikata-wm-894a4e1ee346]

Also known as: Helmet, Sportsmatic

Specifications

Movement

Hand-Winding

Case Material

Hardlex-Coated Steel

Case Width

35mm

Case Thickness

15.1mm

Lug Width

20mm

Crystal

Sapphire

Bezel

Inner Rotating

Water Resistance

180m

Dial Color

Blue Sunburst

Jewels

30j

Frequency

28,800 bph

Power Reserve

67 hours

Year

1981

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