I admit i am far too uneducated to talk about manufacturing processes... it combines with my lack of interest in the subject. I always thought the people were more interesting and worth researching.
If you have a bit more notions in manufacturing, you might enjoy these pictures.
First, the clay models.
Notice there is 2 different possibilities here Mr. Stern thought about.
The top 2 and middle right are the different views of one clay model.
The bottom 2 and middle left are the different views of another clay model.
(see later, how the shape got corrected on paper).
Here the original drawings with pencil corrections: