This is a1920 set of 6 "Automobile Engineering" books by the American Technical Society of Chicago.
These black softcovers with a total of over 2500 pages and 1500 illustrated engravings are marked,as "General reference books for repair men,chauffeurs,and ownwers covering the construction,care and repair of pleasure cars,commercial cars and motorcycles,with especial attention to ignition,starting,and lighting systems,garage design and equipment,welding and other repair methods".
Contentincludes explosion motors,gasoline,steam,electric,and commercial automobiles,as well as motorcycles and gasoline tractors.