Minifon dictating machine model P55-S with Protone-Minifon microphone, 1966.
The Minifon P55 miniature portable wire recorder and dictaphone was manufactured by Protona in Hamburg, West Germany from 1955 to the mid 1960s. The Minifon P55 was originally designed as a portable dictating machine for traveling salesman, the small size being able to fit in a pocket so that it could be taken ‘on the road’. However, this didn’t take off. Instead, it achieved much more success as a covert recording device for private investigators, detectives, intelligence operatives, and spies. It had a recording time of 2.5-5 hours ('short' vs 'long' mode), which, compared to other devices on the market at the time, was very long.
Before magnetic tape was available, speech was recorded on magnetic wire, in this case very fine 0.005 mm diameter nickel-chrome wire. At the time, this machine was the smallest wire recorder available.