Here's a piece I cut and pasted from Wikipedia about Colombo's cars.
Columbo prefers to drive a dirty 1959 Peugeot 403 convertible (which is equipped with a police radio), rather than an official LAPD car while on duty. Peter Falk selected the car personally, after seeing it in a parking lot at Universal Studios. In the show, Columbo boasts that the car is a rare automobile, as it really was: from June 1956 to July 1961 only 2050 were produced, and only 504 were produced for model year 1959. In the episode "Identity Crisis", Columbo tells the murderer that his is one of only three in the country.
Columbo damages the car at least four times: in "Make Me a Perfect Murder" when he t-bones one police car and is hit from behind by another while trying to repair his rear view mirror; in "A Matter of Honor" when he rear-ends another car; in "Caution: Murder Can Be Hazardous to Your Health" when it takes him three tries to crash into the killer's car; and in "Old Fashioned Murder" when he crashes into the back of a police car as he arrives at the murder scene. He also has many other problems with the car.
During the show's initial run on NBC, the license number was 044-APD. The car was sold after cancellation of the series, and when the show resurfaced on ABC in 1989 a similar car was found in Ohio, and received a new license plate number, 448-DBZ.