Seiko Cal. 6640 - 661

The 6640-661 is a sought-after Quartz piece from Seiko's golden era. Powered by the 6640 caliber with 30j jewels beating at 21,600 bph, it delivers a 71 hours power reserve. [seikata-wm-aa443f76092d]

Also known as: Helmet

Specifications

Movement

Quartz

Case Material

Gold-Plated

Case Width

38mm

Case Thickness

11.9mm

Lug Width

19mm

Crystal

Sapphire

Bezel

Inner Rotating

Water Resistance

60m

Dial Color

Black

Jewels

30j

Frequency

21,600 bph

Power Reserve

71 hours

Year

1968

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