In my source, a magazine, the picture appeared earlier. Probably it was a predecessor model, of the Mercurio. For example, the engine block looks like a other model. Please search for another date.
To the connection between Gilera and MV Agusta: Piero Remor and Carlo Gianini developed in 1923 the first transverse 4-cylinder racing engine for motorbikes. In 1935 Gilera took over the project, the famous "Rondine". Due to the ban on compressors after the Second World War, Remor had to overhaul the engine. Due to various problems with and at Gilera, he changed in 1949 to MV Agusta. He is said to have forgotten, to take the blueprints of the 500/4 engine out of his file cabinet....