And, come to think of it, it does look like an Atlas. On the other hand, the nozzle-exit diameter of the F-1 being about 12 feet, the diameter of the rocket is more like that of the Saturn I than the Atlas.
Difficulty: the little spaceplane/landing boat at the top was originally designed specifically to fit on the Atlas, so it is presumably the same size, with the proto-Centaur upper stage being ten feet in diameter.
I now suspect that the figure caption is wrong in describing the main engine as an F-1.
That means this Launch rocket has diameter of 3 meter or 10 ft.