This turned up at a local auction (Fairfield Co. OH).
The July 1916 copy of "The Foundry" stated: "The Wooster and Canton O. plants of the Hinderer Bros., patternmakers and manufacturers of steam and hot water boilers, will consolidate under the firm name of the Canton Pattern and Foundry Co. The company will erect a foundry, one story, 60 X 85 feet, and a pattern shop and storage, two stories, 50 x 60 feet, both of brick and concrete construction.
The September 1916 "The Heating and Ventilating Magazine" noted: "Hinderer Bros., Canton, O., which was recently incorporated with a capitol stock of $20,000, to manufacture steam and hot water heating apparatus, is building a plant in Canton which will employ at the start 25 men.
The November 1919 "The Iron Age" reported: The Hinderer Bros. Co., Canton Ohio, has commenced the erection of a new foundry, 80 x 140 ft., doubling the present capacity.
So it's possible that they could've cast this themselves. For a #6 it's quite heavy at just over 4lb.; there are flow marks between the heat ring and the radius; and the finish grinding around the rim is somewhat jumpy.