1969 was a three-way race. Zenith announced its El Primero calibre first, in January of that year. A consortium of Heuer, Breitling, Hamilton-Buren, and Dubois-Depraz followed two months later with the Chronomatic. Seiko, working independently in Japan, seemed to arrive last — its calibre 6139 didn't officially go on sale until 1970. For decades that made Seiko the answer to the trivia question nobody asked: who came third?
But serial numbers tell a different story. Surviving 6139-6000 models bear production dates from February and March of 1969, which would put actual Seiko chronographs in customers' hands before either rival's calibre reached a finished watch. Seiko nicknamed the line "Speedtimer," and the name lives on in this SBDL109 — a modern solar chronograph that inherits the layout established by that contested 1969 movement: a single sub-dial, a tachymeter bezel, and a case built to survive being used rather than just worn.
