The curiosity and the interest of collectors for watches with an Explorer dial has been constantly increasing since 1953. The Explorer was described as "The reinforced Rolex". It has been used in the Arctic, the Himalayas and the Tropics. Designed to give accu-racy under the toughest out-of-door conditions. The first reference of the Explorer was 6350 and seems to have been replaced by the 6150 model being 2 mm. larger, within a year or two. Produced until 1959, it was replaced by the reference 6610 which bears a flatter back and the 1030 caliber and signed Chronometer on the dial. The next generation of this model bears reference number 1016, then another version was launched with reference number 1655 in the 1970s until 1982, followed by reference number 16550 from 1983 to 1988. This model was called "Explorer II" (also called "Steve Mc Queen" by collectors). Created for speleologists, the additional red hand helps the user to distinguish the nocturnal from the diurnal hours. The latest models were produced with reference number 16570 and 14270 at the beginning of the 1990s. Similar watches are published in "Collecting Rolex Wristwatches", by Osvaldo Patrizzi, Guido Mondani Editore, Genova 2001, pp. 342-347.