CIT (Compagnie Industrielle des Téléphones) 1958 from France. In use with la Poste, beside the wellknown U43. Many technical parts are the same.
The shell is made of bakelite. The handset is made of a thermoplast, probably ABS.
This phone was nicknamed crapaud, toad. Not very flattering.
The big switch at the front is probably not original to the phone and is not directly connected to the phone itself.