Seiko Cal. 6640 - 831

This Spring Drive model from 1985 features a 36mm Hardlex-Coated Steel case. It features a Navy dial protected by a Mineral crystal and offers 40m of water resistance. [seikata-wm-97845e78e97f]

Also known as: World Timer, Emperor

Specifications

Movement

Spring Drive

Case Material

Hardlex-Coated Steel

Case Width

36mm

Case Thickness

11.3mm

Lug Width

18mm

Crystal

Mineral

Bezel

Inner Rotating

Water Resistance

40m

Dial Color

Navy

Jewels

23j

Frequency

21,600 bph

Power Reserve

55 hours

Year

1985

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