The cars all have left-hand drive, and they drive on the right side of the street, but in British Hong Kong, they'd have right-hand drive, and drive down the left side of streets.
At about 40 minutes when Illya arrives disguised as the auction buyer, when talking his voice sounds as if it has been put through a speaker and is unnatural, but the other voices sound normal.
Suspension cable visible during first fight between Richard Kiel and Glenn Corbett.
The boat girl is not named in the dialogue, but she is credited as Jade. However, her code name is mentioned a couple of times as Apricot.
In the 1960s any Westerner in the HK police would not be in any rank lower than Lieutenant. Especially one as educated as "Sgt" Fauntleroy seems to be.