Before the pocket-sized Nagra was created, the Telefunken Minifon P55 was the smallest wire recorder on the market. It achieved success as a dictaphone and covert recording device for private investigators, detectives, intelligence operatives and spies. It enabled recordings ranging from two-and-a-half to five hours (in 'short' or 'long' mode), longer than other comparable devices on the market.

Almost forgotten today, magnetic wire recording technology had its moment in the mid-20th century before being swept aside by the advent of magnetic tape. Although the fine wire made it a very compact medium, it was difficult to handle, and breaks and snarls were common.