Seiko Cal. 4431 - 637

Seiko 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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