The Junior Lecturers Series was produced by W. Butcher & Sons, London (1870-1906) under the trade name of Primus. The slides were sold as a set of eight in a cardboard box. The prize of each set was initially about two shillings but at the end of World War I the price had more than doubled. Size of the slides: 8,2 x 8,2 cm (3 1/4" x 3 1/4").

The complete series was divided into three series, A, B and C.

Series A was described as 'comic tales and nursery stories, with reading on the slides'. Series B and C had readings printed on paper lecture notes. Longer stories required two or more chapters, always multiples of eight slides. The glasses are fitted with a protective glass and black paper binding tape. The images were either circular or square with rounded corners.