Unidentified actors
From the identified credited actors it seems as though people are credited for non-speaking background roles (Canalejas, Brendel) or barely appearing identifiably (Orengo), so the credited roles could belong to practically anybody in the film.
The only scene that looks like it
may have been shot in Italy is the one seen in images 28-35. This is based on the only identified actors here being Italian, such as Feliciani, Ribulsi, Ellis and particularly generico Barozzi, none of whom appear elsewhere in the film.