The Toronto, Hamilton & Buffalo had 110 miles of track in southern Ontario near the New York border, and was co-owned by the Canadian Pacific Railway and the New York Central. These were 70-ton, 2,773-cuft, 3-bay hoppers built by National Steel Car in September 1960. They were put into service in January 1961 as road numbers 1200 through 1249. Thirty of the 50 cars saw international pool service between Dane, Ontario and Pittsburg, PA as well as Cleveland, OH. So there is my loose tie-in to the area I model, although a few decades too late. The ore carried by these cars was primarily reddish pellets 3/8" in diameter with a smaller percentage as 3/16" diameter or less.
(external link: prototype photo)