Seiko Cal. 4431 - 637

The 4431-637 is a sought-after Spring Drive piece from Seiko's golden era. Powered by the 4431 caliber with 30j jewels beating at 36,000 bph, it delivers a 66 hours power reserve. [seikata-wm-e49380bebdfc]

Also known as: Tuna, Panda

Specifications

Movement

Spring Drive

Case Material

Gold-Plated

Case Width

39mm

Case Thickness

15.3mm

Lug Width

21mm

Crystal

Mineral

Bezel

Bidirectional

Water Resistance

160m

Dial Color

Cream

Jewels

30j

Frequency

36,000 bph

Power Reserve

66 hours

Year

1967

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