When exactly started Pininfarina to work for Ferrari?
The very first PF bodied Ferrari chassis is 0177 E, a 212 Inter Cabriolet and PF completed it on the 23rd June 1952. Marcel Massini
In May 1951, in a restaurant of Tortona ( halfway between Torino and Modena ), it took place the first meeting between Battista Pininfarina and Enzo Ferrari. During that lunch, Ferrari and Pininfarina decided to start their lucky partnership. In that occasion Pininfarina sr. , commissioned his son Sergio 25 years old ( sitting at the same table ) to personally take care of the relationship with Ferrari.
This information (although less specific, no one could match Mr Massini encyclopedic knowledge ) is mentioned in Etienne Cornil's book, "Ferrari par Pininfarina", which I checked before I read the above post.
The correct name of Pininfarina Sr. was : Giovanni Battista Farina . ( not Batista...) As well known, he changed his name to "Battista Pininfarina" in 1961, as a result of a special act of the President of the Italian Republic.