Seiko Cal. 6637 - 403

The 6637-403 is a sought-after Spring Drive piece from Seiko's golden era. Powered by the 6637 caliber with 18j jewels beating at 36,000 bph, it delivers a 55 hours power reserve. [seikata-wm-f18eb889c4b6]

Also known as: Bullhead

Specifications

Movement

Spring Drive

Case Material

Hardlex-Coated Steel

Case Width

40mm

Case Thickness

15.7mm

Lug Width

19mm

Crystal

Sapphire

Bezel

Bidirectional

Water Resistance

180m

Dial Color

Blue Sunburst

Jewels

18j

Frequency

36,000 bph

Power Reserve

55 hours

Year

1965

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