Seiko Cal. 6640 - 991

Seiko 6640-991

The 6640-991 is a sought-after Hand-Winding piece from Seiko's golden era. Powered by the 6640 caliber with 29j jewels beating at 21,600 bph, it delivers a 51 hours power reserve. [seikata-wm-b58e5083f8b4]

Also known as: Sumo, Tuna

Specifications

Movement
Hand-Winding
Case Material
PVD Black
Case Width
42mm
Case Thickness
11.9mm
Lug Width
18mm
Crystal
Hardlex
Bezel
Inner Rotating
Water Resistance
60m
Dial Color
Silver
Jewels
29j
Frequency
21,600 bph
Power Reserve
51 hours
Year
1971

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