122 film

The Kodak No. 3A Autographic is one of Kodak’s early folding cameras and was designed to take a variant of 122 format film, commonly known as the postcard format. The specific variant in question is 122 autographic which allows you to use the camera’s metal stylus (seen here held by a metal clip onto the back of the camera) to record information about the photograph you just took by opening the long window underneath the stylus holder on the rear panel of the camera and writing directly onto the margin of the negative via carbon transfer paper. However, since autographic 122 seems to be nearly impossible to find these days, regular 122 film also works.