Hi Frank,
My wife only remembers him from a very young grade school age. She does not know about his occupation or how long he lived. She remembers only that he was in the Army. He never married, but one other thing she does remember going into his house and seeing National Geographic Magazines stacked high off the floor!!
In the Purdue pictures he took a picture of a drawing he made must have been in a drafting class.
There is something below the drawing but I am not sure what it is. It looks like 'maybe' fenders from a car? But why would that be there?
Does this have anything to do with his occupation?????
Charles I'll second a chair.
If you play with the image and "curves" or "shadows" and wildly over expose it you'll probably see detail otherwise hidden.
As to the subject.
These look like illustrations used in manufacture.
Could be one used for pattern making (for casting) just as an overall depiction of a finished part.
There's a lot of cast parts there.
He may have worked in that area and this was part of his training.
All speculation on my part 





















