It was probably customised for a different film and retained by the studio.
The old Hollywood studio system was still in force up until the 1950s. Most films were shot 'on the lot' (in soundstages or on outdoor backlot sets). The studios had large collections of costumes and props, and anything made or acquired for a particular film would go into the collection and be re-used. Sometimes B-movies were written to use sets left over from other productions.
The gothic front-end headlights were designed to look like Checker Cab Manaufacturing, Inc. Chicago fleet's logo. Take a look at the picture of Cary Grant getting out of the green 1956-58 Checker A8 in the movie "North By Northwest". Look at the logo on the door, then look at the front headlights on this Checker Model A and you'll see they match. The Chicago Checker fleet used that logo up until the early sixties.
The 1940 Model A was one of the most innovative taxis ever manufactured in America. The entire rear section of the roof was a steel clam shell that could be opened up for passengers to ride in convertable comfort.
Unfortunately the tools a dies were melted down for the 1940's war effort. Checker did not produce another car until new dies were made in 1947. 99.9 percent of Model A's were built for taxi service. By 1947 most had been run till the wheels fell off. There is only one known survivor, a 1941 Limo, fully restored it resides in New York state.