Seiko Cal. 6631 - 366

The Seiko 6631-366 represents an important milestone in Seiko's 1971 lineup. Powered by the 6631 caliber with 36j jewels beating at 21,600 bph, it delivers a 52 hours power reserve. [seikata-wm-ff11793c5e24]

Also known as: UFO, Baby Tuna

Specifications

Movement

Automatic

Case Material

PVD Black

Case Width

39mm

Case Thickness

9.3mm

Lug Width

18mm

Crystal

Sapphire

Bezel

Fixed

Water Resistance

100m

Dial Color

Champagne

Jewels

36j

Frequency

21,600 bph

Power Reserve

52 hours

Year

1971

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