Seiko Cal. 6631 - 521

The 6631-521 is a sought-after Spring Drive piece from Seiko's golden era. Powered by the 6631 caliber with 30j jewels beating at 28,800 bph, it delivers a 68 hours power reserve. [seikata-wm-22b5c4bd3474]

Also known as: Monster, Crown

Specifications

Movement

Spring Drive

Case Material

Hardlex-Coated Steel

Case Width

36mm

Case Thickness

14.0mm

Lug Width

19mm

Crystal

Acrylic

Bezel

Rotating

Water Resistance

180m

Dial Color

White

Jewels

30j

Frequency

28,800 bph

Power Reserve

68 hours

Year

1978

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