Seiko Cal. 6638 - 560

The 6638-560 is a sought-after Spring Drive piece from Seiko's golden era. Powered by the 6638 caliber with 35j jewels beating at 21,600 bph, it delivers a 57 hours power reserve. [seikata-wm-0f78def1acd6]

Also known as: Sumo, Rally

Specifications

Movement

Spring Drive

Case Material

Hardlex-Coated Steel

Case Width

40mm

Case Thickness

14.5mm

Lug Width

19mm

Crystal

Hardlex

Bezel

Inner Rotating

Water Resistance

50m

Dial Color

Navy

Jewels

35j

Frequency

21,600 bph

Power Reserve

57 hours

Year

1990

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