HI CG the photo that you have is of the early Lancia version of the D50 with the sponson fuel tanks. It is an optical illusion that makes you think it has rear fenders. It is just the rear tires sticking up over the fuel tanks.
Agree the car in post #1 car hasn't got fenders over the rear tyres. It's either an image from early 1956 before Ferrari had modified the Lancias much or a1955 Lancia. It might even be Castellotti's number 30 Lancia seen on the second row of the start at the 1955 Monaco GP in this photo-
This was what made me think of a rear fender, picture taken farther
away. These cars were all mentioned in the article about early F1
and Grand Prix cars and thanks everyone for your feedback. CG