To help alleviate costs, the 18th episode, "The Interrogation", is largely comprised of clips from previous episodes in the series.
There is library footage of Hong Kong harbor. Two naval ships are briefly visible. One looks like a destroyer or cruiser. The other appears to be a USN landing ship. The USS Vancouver (LPD-2) is the only one to have visited Hong Kong (in early 1965) thus perhaps giving a clue to the date of filming.