I have my doubts about there being “small tape recorders” before about 1960.
It’s not quite a PRICK-6 but he could have a radio under his coat, listening to an ear piece?
You are correct. Tape recorders came along in the late 40s, in pocket form in the late 1950s. Google “minifon”. You could get a neat wristwatch microphone for spy work, and a body harness to conceal the recorder under your clothing. The original Minifon was a wire recorder, later a tape recorder.