The "one" in "One Adam 12" stood for the area of the division they were stationed in, "Adam" referred to the type of car they drove (a two-man patrol car) and "12" was for the area they patrolled. However, "one" was the code for Central Division (downtown). Since the unit was shown working in Rampart Division, the actual call sign should have been 2-Adam-12.
The patrol cars in the series were not real LAPD cruisers but were purchased by Universal from Chrysler Corporation and American Motors, and outfitted by the prop department to LAPD cruiser specs. In order, the cars were: 1: 1967 Plymouth Belvedere 383 V8 ("pilot" only); 2: 1968 Plymouth Belvedere 383 V8 (season one); 3: 1969 Plymouth Belvedere 383 V8 (season two); 4: 1971 Plymouth Satellite 383 V8 (season three); 5: 1972 and 1973 AMC Matador 401 V8 (starting in season four).
The dispatcher's voice on the program was that of Shaaron Claridge. Claridge was a real L.A. dispatcher. Producer Jack Webb thought that using a real dispatcher for the voice-overs would lend authenticity to the program. He did the same thing for his later series, Emergency! (1972), casting a real-life emergency dispatcher to voice the role.
Fresh out of the academy, Probationary Officer Jim Reed is paired with veteran Officer Pete Malloy. However, Kent McCord had already appeared as LAPD Officer Jim Reed in several Dragnet 1967 (1967) episodes nearly a year before "Adam-12" debuted.
Malloy's badge number was 744 and Reed's was 2430. Badges are reissued once an officer retires, so the permanent numbers are "Serial Numbers". Reed's serial number was 13985, which would coincide with an Academy class from 1968, the year Reed was supposed to have joined the LAPD.
The car used for Reed and Malloy's close ups was towed by camera car. The car's windshield showed reflections of the camera and crew, so the car's windshield was removed. However, this led to the wind blowing Reed and Malloy's hair, so a shield was created to enclose the camera and front of the car.
During the period that "Adam-12" was filmed, the state of California-issued six--digit vehicle license plates in the letter/number format (i.e., ABC123). The final letter was never I, O, or Q, so that they would not be confused as a number. The civilian vehicles on the show usually have the letter "I" as the final letter, indicating that this is a movie/TV prop plate.
In the first season(s), the officers wear the eight-point hat, and the buttons on their shirt pockets, epaulets on the shoulders were brass, and the jackets were of the wool Melton type. When Edward M. Davis became LAPD Chief, he did away with these items and went with a round hat, antique silver buttons and the Eisenhower type of jackets, which is reflected in later seasons.
While the series used 1 ADAM 12, LAPD units used odd numbers for beats, so they would have been 1 Adam 11 or Adam 13. The only even numbers were used by the supervisors (i.e., sergeants) and they would have been the numbers 10, 20, etc. so 1 Adam 12 would never have been an actual assigned number.
According to the LAPD training officers doing the audio commentary on the Season Two DVDs, the little medallions that Reed and Malloy wear on their uniforms signify their shooting abilities. In the case of Malloy, who has a gold medallion with two bars, he is rated as an distinguished expert shot while Reed, who has a silver medallion with one bar, is a sharpshooter. The commenting officers also explain that police officers are required to be tested on their shooting skills every two years in the LAPD.
In the later seasons Malloy's personal vehicle is a tan AMC Matador coupe. In a few episodes he complains of it "needing to go into the shop". This issue plays a major part one episode from the last season. It's unusual that he has issues with the car, as AMC provided vehicles to the show.
Kristin Harmon, who played Jim Reed's wife Jean during the final season, was actually married to popular singer/actor Ricky Nelson, who also happened to be one of Kent McCord's best friends. In fact, she was billed as Kristin Nelson.