Seiko Cal. 6631 - 391

The 6631-391 is a sought-after Spring Drive piece from Seiko's golden era. It features a Black dial protected by a Acrylic crystal and offers 50m of water resistance. [seikata-wm-a876fce1b6c1]

Also known as: UFO

Specifications

Movement

Spring Drive

Case Material

PVD Black

Case Width

35mm

Case Thickness

9.0mm

Lug Width

19mm

Crystal

Acrylic

Bezel

Coin-Edge

Water Resistance

50m

Dial Color

Black

Jewels

22j

Frequency

21,600 bph

Power Reserve

63 hours

Year

1973

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