In the opening scene, Illya and Napoleon are pursued by several small aircraft. They are Bensen B-8 Gyro-Copters.
The scene where Solo and Kuryakin park outside of a group of buildings to vist Dr. True at his laboratory was filmed at the TRW Space Park campus in Redondo Beach, California.
The song played by Every Mothers' (sic) Son, "Come On Down to My Boat", was their only Top 40 hit, peaking at #6 on the Billboard Hot 100 in July 1967. The group did have two more songs on the Hot 100 that year, one peaking at #46 and the other at #93.
Extracting gold from sea water was considered a viable idea after WW I, when a German scientist thought it would make it easier for Germany to pay off its reparation payments. The plan was abandoned after several experiments when they realized the amount of gold in sea water was just .001 as much as they had originally thought, making the scheme worthless.