Just like the Radiomir, the original Luminor watches got their name from the luminescent paint compounds used on their dials. In 1949, Panerai switched from radium-based paint (which is now understood as being highly radioactive and toxic) to Luminor, a safer tritium-based paint that is also more luminous.
In 1950, Panerai released the Luminor – a case characterized by its crown-protecting bridge, wire lugs created from the same block of steel as the case, a 47mm cushion-shaped case similar to the Radiomir 1940 and a flat wider bezel.
When Panerai watches became available for sale to the public in 1993, designer Alessandro Bettarini (Panerai’s chief of mechanical engineering at the time) created the modern Panerai Luminor. He brought back the crown-protector bridge and the Luminor name from the archives, but with a smaller 44mm case.