Berto?
Yes! Carrozzeria Berto it is!
You won't find this info anywhere and I'm in contact with the owner of this car. He knows nothing about it.
I found 2 people knowing the story behind it: a guy who provided the engine and a guy who knows about the building process.
This kind of cars is quite misterious because in Italy it is not 100% possible to register a car like this in the first place: you need documents and papers of a donor car and your car will assume the identity of it, even if you now have a sport and the papers reports a sedan! In addition to that, too many times sellers and co. make up a fictional story about the car (not saying this is the case for this very car...) pretending they found an original barchetta in some barn and restore it. This generated over the years a feeling of hate agains them. I like them all and in my opinion the car itself has no fault in that.
Well done Wendax!