The 1680 broke the Submariner in two. The first Sub with a date, and with the cyclops lens that purists swore ruined the dial, it arrived at the end of the 1960s - sources record the introduction as 1967, 1968 or 1969, and the file marks it accordingly. The market settled the aesthetic argument fast: within a decade the date model dominated, and the no-date became the minority taste it remains.
The earliest dials printed SUBMARINER in red, and those Red Subs became one of vintage Rolex's defining trophies, partly because the red dials were routinely replaced with white-text service dials during maintenance. Many 1680s that were born red exist today in white, which makes an original red dial the whole value of the watch that carries it.
The reference where a dial is worth more than the watch around it. On any Red Sub, the dial's originality is the entire question: era-correct printing, correct patina, and a serial that agrees with the red-dial production window. A white-dial 1680 is the honest, attainable way into the first Submariner Date.
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.