It was a coincidence that I checked the Siata's that are currently for sale, and found this one. The book that I have from Fornai did not have this car in it. The super testa is well described, but this model was not pictured, and its model is clearly post 1950, not a 40 model. as the body was beleieved to be made in 1955, it is very much a mixture of the 300BC and the 208, which are gorgeous spiders.
According to my info some Siata Springs were later converted into barchetta models, I first believed this was one of them as well.