Here is an interesting report summarizing cigarette advertising on TV by a graduate student and professor at the University of North Texas:
http://www.rtvf.unt.edu/people/craig/pdfs/tvsmoke.pdf
It states that the cigarette ad ban on TV in the U.S.A. went into effect midnight, Jan. 1, 1971. If a station was airing cig ads after that they may have been just trying to sneak past the ban hoping they wouldn't get caught.