Sorry to say that, but Spider's answer is not 100% correct.
The car is the Moretti 700 4C. The engine was actually made by Giannini and is a prototype of 4-cyl. boxer 700 cc (not 750).
The chassis is indeed Fiat (from the 500 F), but the car was never been told as a Fiat, nor a Giannini.
It was marketed by Moretti and after a few (probably only 2) units with the 700 4C unit, some more were built with the original Fiat 500 engine, as the Moretti 500 Coupé.