Daily Dose of Dr. Odd: a Lovely Bit of Slightly Mysterious Design

JF Ptak Science Books  Quick Post

Care to have a guess on the derivation of these designs? Well, I guess the indicators give this away, but had "elevation wheel house cover" not been printed in the it might have been harder to figure out what this simple and lovely thing is. 

And this:

They come from George J. Mercer's Motor Body Engineering work, printed and published by the author in the very front yard of American auto production--Detroit.--in 1947, when that city owned the 6,000-pound world. 

And so:

And this:

Neat little puzzle.