I couldn't remember this car and, sincerely I was completely wrong way going, perhaps because I'm quite sure that this barchetta has been restored with lot of fantasy so that it looks a Colli '40s product just for a little.
Anyway, from the plate I found a note in my archive were I registered this car as a Fiat 500A elab. Siata; I can't remember the source of this note.
I'm pretty sure this car is not a proper Siata, perhaps it has a Siata head.