The Panerai Luminor was first introduced in the 1950s, as an evolution of the older Radiomir design. While the Radiomir was a relatively simple time-only dive watch design, the Luminor added the now-iconic lever-operated crown protection system. This was designed to prevent divers from accidentally pulling out the crown while underwater - something which would've led to a catastrophic failure of the watch's movement. Only in 1993, however, did Panerai begin offering this watch to the open market. Since then, it's become an iconic part of the brand's heritage.