I have seen it described as Bisiluro 955/3. It had a Giannini engine so some tidy-minded people might describe it as a Nardi-Giannini Bisiluro 955/3 which competed at Le Mans in 1955.
I don't speak Italian, but I believe "bisiluro" translates as twin-boom, twin-torpedo or twin-hull in which case it is a description and not a model designation and should not be capitalised.