Seiko Cal. 6640 - 581

The 6640-581 is a sought-after Hand-Winding piece from Seiko's golden era. Powered by the 6640 caliber with 21j jewels beating at 21,600 bph, it delivers a 52 hours power reserve. [seikata-wm-a9dc58d59ab4]

Also known as: Sumo

Specifications

Movement

Hand-Winding

Case Material

Titanium

Case Width

42mm

Case Thickness

12.3mm

Lug Width

20mm

Crystal

Sapphire

Bezel

Bidirectional

Water Resistance

90m

Dial Color

Green

Jewels

21j

Frequency

21,600 bph

Power Reserve

52 hours

Year

1987

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