Click-clack! Click-clack! This Mignon 4 is a mechanical index typewriter.  

A German company called Allgemeine Electrizitats Gesellschaft (AEG) produced the original model of the typewriter in the early 20th century. It sold the Mignon 4 in the 1920s and 1930s.  

Mechanical index typewriters like the Mignon 4 had a pointer or stylus that let a typist choose a letter from the index. One hand moved the pointer across the index, while the other depressed the machine’s printing key to print the letter on paper.  

The Mignon 4 had two other keys: the left-hand key was the space key, and the right-hand key was the backspace key.  

AEG sold its typewriters in various countries, including the United States. The Mignon 4 is one of about a half-dozen typewriters in the FBI's historical collection. The FBI Laboratory secured devices like the Mignon 4 in the 1930s and 1940s as the FBI broadened its intelligence work.