Luminor gets its name from a luminous material made of tritium. Panerai developed this material in the 1940s and patented it in 1949. It replaced the radioactive material Radiomir, the namesake of their other watch series. Around this time, the Florentine manufacturer presented the first Luminor watches with crown-protecting bridges, which kept water from soaking into the inner parts of the case. The mechanism was particularly suitable for manual movements, which need to be wound regularly. The watch's caliber was made by the Swiss manufacturer Cortébert.