This episode has a climactic scene in the BART 16th Street subway station on Mission Street. The station was still under construction and brand new when this episode was filmed in 1972. The station didn't open to the public until November 3, 1973.
During the Act lll rooftop chase the Transamerica Pyramid is featured prominently in the background - the building had just been completed in summer 1972, shortly before this episode aired in September of that year.
When Dr. Ford said that Gus was "a sure D.O.A.," it was possibly the scriptwriter paying homage to actor Edmond O'Brien, who played Frank Bigelow in the film noir classic D.O.A. (1949).
Karl Malden and Edmond O'Brien served together in the 31st Army Air Force Base Unit in World War II.
Although Mike Stone wears a hat throughout the series, men in the U.S. stopped wearing hats in the 1960s, mostly attributed to the fact that JFK did not wear a hat at his inauguration.