It is known that after the italian armistice in 1943 all the material and all the documentation about the CS 15 were confiscated by German military authorities and moved to Germany.
Thank you for the kind replies. An AS.8 engine in perfect shape is presently on display at the Rivalta factory of Avio Aero (former Fiat Aviazione) in Turin. A rather extensive description of the CS15 design is in O.Marchi, "Il superamento del primato di Agello" - Rivista Aeronautica, n.5, 1980.