When the diamond cutter asks at the hotel desk for the room number of Harold Streeter, he is given, in German, the number 371. Later, when Hugh Lockwood calls the room of Harold Streeter, he asks for room number 397.
The flight that Lockwood and Streeter take at the beginning of the film changes from a 707 to a 747 apparently in mid-flight.
When the diamond cutter (Ben Wright) asks at the hotel desk for the room number of Harold Streeter (John Gielgud), he is given, in German, the number 371. Later, when Hugh Lockwood (Hugh O'Brian) calls the room of Harold Streeter, he asks for room number 397.
In German (and Austrian), the letters "ei" sound like "I' (like myself), and "ie" is pronounced like we would pronounce "ee" (like need). So, when Kurt Van Niestatt (Kurt from Noplace, essentially), pronounces it "Nicestatt," he pronounced his own name wrong.
A piece of stock footage showing a 707 taking off is played at the wrong aspect ratio.