Seiko Cal. 3866 - 661

The 3866-661 is a sought-after Spring Drive piece from Seiko's golden era. Powered by the 3866 caliber with 31j jewels beating at 36,000 bph, it delivers a 63 hours power reserve. [seikata-wm-a979bc84cb61]

Also known as: Sumo, Sportsmatic

Specifications

Movement

Spring Drive

Case Material

Gold-Plated

Case Width

37mm

Case Thickness

14.8mm

Lug Width

19mm

Crystal

Mineral

Bezel

Inner Rotating

Water Resistance

190m

Dial Color

Champagne

Jewels

31j

Frequency

36,000 bph

Power Reserve

63 hours

Year

1976

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