The California Highway Patrol strongly supported the program in its first two seasons, and the production company was able to rent actual CHP squad cars. Generic "Highway Patrol" logos were placed over the real CHP emblems and studio license plates were taped over the genuine "E" (exempt) plates. The 1955 Buick Century two-door sedans seen were built especially for the CHP and were never offered for sale to the public. Two-door sedans were adequate because the real CHP rarely arrested anyone at that time, being involved more with accident investigations, enforcement and auto thefts. Major police powers were not invested in the CHP until 1964. The show's uniforms were copies of the khakis worn by the CHP including the state seal and the slogan "Eureka", except that the word "California" was removed. Authenticity was a major goal, and Dan Matthews' call sign - 21-50 - was the actual unit number of then-CHP Commissioner Bernard Caldwell. In mid-1956 the CHP dropped its support of the program over differences in story lines and presentation, and refused to supply any more squad cars. The producers quickly acquired an incorrect Buick Super four-door hardtop to complete that season. Accurate squad replicas were ordered for the 1957 season, but the 1958-season cars differed from reality. The trailer hitches seen on the squad cars were for towing the film company's equipment trailers to shooting locations. Brand names of suspect vehicles were never scripted; they were always described as "a green coupe", "a tan station wagon" or "a dark-blue sedan".
