Seiko Cal. 6643 - 428

The Seiko 6643-428 represents an important milestone in Seiko's 1985 lineup. It features a Green dial protected by a Sapphire crystal and offers 60m of water resistance. [seikata-wm-b4f3139a2bcf]

Also known as: Sumo, Helmet

Specifications

Movement

Hand-Winding

Case Material

Two-Tone

Case Width

44mm

Case Thickness

12.1mm

Lug Width

20mm

Crystal

Sapphire

Bezel

Bidirectional

Water Resistance

60m

Dial Color

Green

Jewels

26j

Frequency

21,600 bph

Power Reserve

70 hours

Year

1985

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