Mr. Dugan is the director/whatever of the veteran's hospital. His position wasn't stated, but he had his own office, and was dressed professionally as in shirt, tie, jacket, etc. He could have been a mid-level clerk hired to speak with visitors, or to handle inquiries, or even a psychologist, but he wasn't in doctor attire. I guess safer to say "veterans hospital employee with some authority."
He showed John Black the military record and dogtags that the veterans' hospital system had for Dick Van Dyke's character. Mr. Dugan was sincere, professional, and helpful. He gave out only the military record on file, but didn't disclose medical records. (The prewar identity in the military file had been incorrect for 70 years because the dogtags had been switched 70 years ago; but Mr. Dugan and the veterans system didn't know that.).
This character "Mr. Dugan" appeared for only one episode, but he was very significant to the Dick Van Dyke storyline! I don't think he'll air again, but you never know.
BTS pic from the actor's instagram: