Seiko 6139-7100 "Stormtrooper" was in production approximately from 1970 to 1977, a run of approximately 7 years, carrying the 6139 automatic chronograph caliber in a 40 mm case rated to 70 meters.
The clean minimalist of a loud family - quietly under-collected and often the best value in the line.
Dates carry a "c." because that is what honesty requires: Seiko's own archive gives only approximate production windows by caliber, so the file states the documented range and marks it as such rather than inventing precision.
The full collector's file for this reference — variants, dial codes, and the authentication walk-through — is on the writing schedule; the specifications above are the permanent record.
The 6139/6138 family shares a parts bin, and fifty years of donors have kept it circulating: dials, bezels, subdial hands and pushers swap freely between models, and redials chase every famous nickname. The rules: the caseback serial dates the case to a month, every visible part must belong to that era and that specific model's catalog scheme, and original-but-worn outranks refinished-and-shiny at any price. The Seiko serial decoder on this site works for every reference in this family.
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.