In this picture Mussolini appears not to have shaved his head yet so my (educated) guess would be the early '20s...

...sometime after 1922 anyway, for the caption describes him as "His Excellency [the Head of Government]".

It would help of you transcribed the information on the card, as it is unreadable. Fyi, the Fascist Party used a dating system "year of Fascism" that had year one starting in 1922.

I can't read what it says in the lower-left hand corner. Can anyone else make it out?