Don Marshall

 portrayed McMann & Tate account executive Keith Wilson in the seventh season episode, "Sisters at Heart" (1970).

Biography
Don Marshall's heyday was on the small screen in the 1960's and 1970's. The athletic and clean cut actor is best remembered as first officer and co-pilot Dan Erickson in Irwin Allen's ground-breaking science-fiction series Land of the Giants (1968). Having excelled at football, pole vaulting and other sports at college, he happily undertook most of his own stunt work. Along with Nichelle Nichols ("Star Trek: The Original Series" 1966) and Greg Morris ("Mission: Impossible" 1966), Don was one of the precious few African-American actors of that period to be regularly featured as a prime time lead on screen.

Don had started out as an engineering student in the mid 1950's and took up acting on the advice of a friend. He studied drama at the workshop of Hollywood acting coach Robert Gist and pursued theatre arts at Los Angeles City College. Following brief stage experience, he then segued into television. His acting career still nascent, he landed a small role (as a marine engaged to Nichelle Nichols) in an episode of The Lieutenant (1963), a short-lived venture produced by Gene Roddenberry. A few years later, he was again recruited by Roddenberry to play the part of astrophysicist Boma for the Star Trek episode "The Galileo Seven" (reuniting him with Bob Gist who served as director). Don was given the chance to show his acting credentials in several powerful scenes interacting with Leonard Nimoy.

In subsequent years, he busied himself with roles on many diverse kinds of television shows ranging from Daktari (1966) and Ironside (1967) to Julia (1968). On the big screen, he acted in the violent 'blaxploitation' prison drama Terminal Island (1973) and was one of the leads in the schlock sci-fi outing The Thing with Two Heads (1972). By the mid 1970's, plum roles became relatively scarce and Don focused on running his own production company (DJM Productions) which specialised in turning out commercials and documentary subjects. Latterly, Don became a regular attendee of sci-fi conventions where he always spoke appreciatively of the genre and of Roddenberry in particular.

Source
Don Marshall on the Internet Movie Database. Retrieved on December 9, 2019 and January 31, 2020.