Mr Phelps was briefed using a "Mini-tape Recorder".That same year, Philips Electronics actually produced the very first mini tape recorder in 1967, when this episode was filmed. This model eventually lead to cassette tape recorders a few years later.
The confidence trick used on Walter DuBruis, "the money box," is one of the oldest in the various books devoted to describing such scams. Here, the Impossible Missions Force "jazzes it up," computer style.
Cinnamon is given a modified cigarette lighter which serves as a switch, has the ability to activate low-level microwaves emitters via remote control. Any document printed using microwave sensitive ink, upon being bombarded with said microwaves , will be reduced within seconds to a greasy, illegible mess.