Strangely, the official MM database says it was a Fiat 500 and raced in S750 category
That is the hardest problem with those database. You will find only tens of Fiat 500 and 1100 but not the name of the specialist who modified it. That is because the car was registered at the race as a Fiat. A lot of minor racer firms disappeared and there is no sign of them in those lists.
About the Sail, I was wrong, my book reports that a Sail 1100 Barchetta raced the 194
9 MM, #505, a nice car indeed.