I don't know the name of the actor, but in the Jack Webb lobby card the guy on the right was in a number of later "Dragnet" show episodes. If you watch the later series (1967, 1968, etc.) Webb was very loyal to his other actors. Most of them appear in episode after episode in various roles, and then show up on his other show "Adam-12".

Robert, if you are a fan of the show itself, I may have something of interest.