The Root Beer starts here: the steel 1675 rebuilt in steel and yellow gold around 1970, with a brown-and-gold bezel and the matte brown dial whose raised gold markers gave collectors the name nipple dial. The whole line's identity, brown where every other GMT is red and blue, warm where the family is cold, was set by this reference, and its nickname came later, from the drink the colors resemble. Caliber 1575, acrylic crystal, and the same case as its steel parent, which is exactly how the file's lineage renders it: a branch off the 1675, not a separate species.
Bezel colorways varied across the run, brown with gold, brown with silver tones, and faded examples now trade on their patina, which invites the era's usual traps: reproduction inserts chasing ghost-bezel money, and relumed or replaced nipple dials, whose markers are fragile and frequently damaged by careless service.
The founding Root Beer trades on warmth and originality: honest patina on dial, bezel, and gold beats restored shine every time. The nipple markers are the fragile part and the value part, which is the usual vintage arithmetic.
Production windows and specifications compiled from documented collector references and period catalogs, cross-checked across independent sources; manufacturer records for this era are approximate by Seiko's own account.