Seiko Cal. 6638 - 400

The 6638-400 is a sought-after Spring Drive piece from Seiko's golden era. Powered by the 6638 caliber with 31j jewels beating at 28,800 bph, it delivers a 43 hours power reserve. [seikata-wm-8a494a6f0047]

Also known as: Tuna, Sportsmatic

Specifications

Movement

Spring Drive

Case Material

Titanium

Case Width

37mm

Case Thickness

13.0mm

Lug Width

20mm

Crystal

Acrylic

Bezel

Inner Rotating

Water Resistance

40m

Dial Color

White

Jewels

31j

Frequency

28,800 bph

Power Reserve

43 hours

Year

1975

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