How the Seiko 5 Became the Ultimate Starter Watch | Gear Patrol
https://www.gearpatrol.com/watches/a81663/seiko-5-watch-history/
WebMar 6, 2022 · In fact, the watches have been signed several different ways — Seiko 5, Seiko 5 Sports, Seiko Sportsmatic 5, Seiko 5 Actus — and used a range of different automatic movements. When it was introduced in 1963, the Seiko Sportsmatic 5 heralded multiple innovations. The first was the Diaflex mainspring, Seiko’s unbreakable mainspring.
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