Alfredo uses a silent Super 8 camera and silent film stock to shoot the movies in his flat, but when we see him watching the results on a projector some days later, the movie has sync sound that was seemingly recorded at the time of the shoot.
The type of Kodachrome cartridge we see cannot have existed at the time of action: only since the end of the 1990s did European Kodachrome cartridges have their serial number printed on the label with black ink, prior to that the serial number was dry-stamped on the label.