: Rolex forced to recall the 6542 GMT-Master by the US AEC for possibly using Strontium 90 as luminous material in the bezel.
Late 1958 into 1959
: The appearance of the Exclamation Point on some non-Crown Guard models along with "radiation safe" sticker.
: The re-appearance of the Exclamation point on Crown Guards models & early 1016 Explorer which was not
on the first generation dials.
Late 1962 into all of 1963 and perhaps early 1964
: The Underline appears on many Rolex models across all lines, Dress & Sport & Chrono.
Mid-1964 at the latest and on
: The disappearance of all these extraneous markings and the standardization of "T" markings down by the SWISS on all Rolex dials across all models, "T SWISS T" for lower luminous models and "SWISS T-25" for the Tool watches with super luminous dials.
Connected? Not connected? And why no Ex Point on the first 1675 and 5512, ca. 1959-60?
These are the so-called "Old Fonts" dials, so maybe they actually previous generation dials fitted into the first models of CG GMT & Sub as well as the 1016?
And of course, this Rolex-only timeline can be cross referenced with all of John Harris's wonderful research into what was happening in the world at large vis a vis radioactivity and the attempt to control its use in civilian applications such as, for example, watch dials.