Vintage Icons: A Seiko 6138 Chronograph Collector's Guide — 60Clicks
1973 Seiko 6138-3002 "Jumbo" Chronograph
Thomas' Timepieces - Seiko 6138-3000 and 6138-3002, both models often referred to as the Seiko Jumbo. The Seiko 6138 was arguably the world's first automatic chronograph (Zenith/Movado El Primo also claimed to