This is a Pere Marquette Railway Crane Diagram Book dated August 1946. Railroads issued diagram books such as this for freight and passenger cars, steam locomotives, cranes, floating equipment, etc. They were used in a variety of purposes. They were a ready reference publication that could be used by the accounting department, mechanical officials, maintenance officials and workers, foremen, agents, and for freight and passenger cars even sales representatives and officials. Printed with the standard "blueprint" diazo process, the pages were updated as needed and sent to all holders of each book, who destroyed the old page replacing it with a new one. This book appears to be intact as issued in 1946.
Note that it was issued by the Advisory Mechanical Committee in Cleveland. This organization was created in 1930 to oversee, consolidate, and standardize mechanical equipment and operations for the railroads under the control of the Van Sweringens. It persisted until about 1947-48 when each road assumed its functions.