At the factory in Modena: X333 behind Guerrino Bertocchi, Omer Orsi, and yes, Juan-Manuel Fangio. It looks like a series II (no rear quarter windows). Dark colour. Could it be one of the factory demonstrators?

X333, ca 1966

Fangio seemed to be more interested in the Mistral...

Bertocchi, Orsi, Fangio.