If I am not wrong, Bracq would have left MB by 1967; so, he might have started it, and Sacco finished it, although seems that the proposal lack some refining or detailing.
In any case, if this proposed car was designed around 1967-1968, it was a pretty old fashioned design by then, too 'Miuresque' of Dino in its curves, while the trend was becoming the wedge -Carabo, or just look at the 1969 Geneva shown first C111.