Trooper "Bluey" Grimsey is credited with designing the LRDG cap badge. The legend has it that a scorpion stung him and then promptly died. (The Scorpion, not Bluey) The emblem is only slightly similar to the Italian Auto-Sahariana Company, which features a crab in a circle.
Originally the cap badge was a brooch that members gave to their sweethearts. They were locally made in the jewelry shops in Cairo. It wasn't long before the brooch was worn on the Black Beret of Royal Tank Regiment. Eventually this became the "official" unofficial head dress of the LRDG.
Typically it features a brass scorpion with the letters LRDG underneath centered in a silver circle.