Seiko Cal. 6638 - 923

Seiko 6638-923

The 6638-923 is a sought-after Automatic piece from Seiko's golden era. Powered by the 6638 caliber with 36j jewels beating at 28,800 bph, it delivers a 58 hours power reserve. [seikata-wm-8a6fe1d1672e]

Also known as: Sumo, Tuna

Specifications

Movement
Automatic
Case Material
Stainless Steel
Case Width
36mm
Case Thickness
14.7mm
Lug Width
21mm
Crystal
Mineral
Bezel
Inner Rotating
Water Resistance
90m
Dial Color
Cream
Jewels
36j
Frequency
28,800 bph
Power Reserve
58 hours
Year
1975

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