There are a number of iterative concept sketches done by American conceptual artist Ralph McQuarrie but what is most important for this effort is the transition from concept art to production blueprints.
The first orthographic view and the first view with dimensions appears on this Ralph McQuarrie illustration. While the view on the left has a familiar looking McQuarrie concept sketch, the view on the right is the first example of an orthographic view of Artoo. The orthographic view sets the overall height of Artoo at 3-1/2 feet (42 inches) and sets the body and dome width of Artoo at 1-1/2 feet (18 inches.)
The next illustration from Ralph McQuarrie is the first complete orthographic blueprint. In addition to the overall height and the width of the body, the overall width is dimensioned as 2-1/2 feet (30 inches.)
Both of these illustrations have the center leg drop moving rearward and the legs moving forward.