This curious object is the Thermator fireless cooker, and it was manufactured right here in Nebraska.
Fireless cookers were popular in the early 20th century, and slowly cook food using less fuel. Food was heated in pots on a stove or fire, and placed in the fireless cooker. Soapstone or metal heating plates were also heated and placed under and over the pots. The cooker was tightly closed to retain the heat and not reopened until the food was presumed cooked. Recipe books gave general guidelines for cooking times.