Every film is signed by the manufacturer.
Alongside the frame numbers at the outer edge of every roll of film, each manufacturer places their name, or the film type - or sometimes both. After a quick search through our storage, we found the first proper Ferrania signature used on films from the late 1950s until 1964. After this, the signature was switched to "Ferrania-3M" and later, simply "3M".
The signature is a mask that is inserted into the perforator and exposes directly onto the edge of the film. In a second step, the frame numbers are exposed using a similar mask. The video below shows both of these steps in slow-motion detail (and of course in the light).