The Rolex Milgauss ref. 1019 was manufactured as an anti-magnetic wristwatch from 1966 until the 1980's for use by particle researchers and members of other professions which encounter high levels of magnetism. Most watches will be affected by magnetism at around 40 gauss (a unit of measure for magnetism); the 1019 remained accurate at 1000 gauss. Hence the name MIL (one thousand) Gauss. The model underwent several dial variations. The first examples had Rolex in smaller print and Milgauss larger; later the word Rolex was larger. The early versions were offered with either a black or silvered dial with luminous hands and outer dots. Later examples, available with silver or black dials, had luminescent material applied directly to the hour markers. This dial variation is thought to have been created in conjunction with the CERN particle research facility headquartered outside Geneva; it was designed without any luminescent material. Tritium, which registers on a Geiger counter, could potentially affect the outcome of precise radioactivity readings. Consequently, the hands and markers were black. Throughout the manufacture of the 1019, the silver dial was available as an option. The present example is the rarest version of the Milgauss 1019, with the above mentioned CERN dial and the small print Rolex text.