Most old cars you see in the movies are owned by private collectors who occasionally lend their cars to movie productions. These collectors always keep their cars spotless, and the set dressers have to dirty them up for the movie.

In the shot were our trio and Baby Face Nelson are getting out of the car(time index 34:36) to rob the bank, only the back and left side of the car would be visible and only those two sides would need to be dirtied -or so the set dresser thought! He forgot that the car had "suicide" doors and that the spotless right door would be visible when opened.