The present watch is part of a small series of diver's watches made by Rolex for Officine Panerai during the 1940s. The engraving "S.M.Z." stands for SoMmoZzatore, the Italian word for frogman.
The model name "Luminor" is taken from the luminous substance based on tritium and used for the numerals and hands on the dial.
Guido Panerai & Figlio, founded in 1860 in Florence, advanced quickly to the official watchmaker of the Italian Navy and produced extremely modern and precise instruments. In 1936 the company, later renamed Officine Panerai, launched the first prototype of a diver's watch.
Most models are equipped with a crown protecting bridge, invented by Panerai in 1943 (patented in 1956). Its main functions are protecting the crown from shocks, compressing the sealing gasket with the lever to make the watch water-resistant to a depth of 200 metres and rewinding the watch when submerged.