Prior to 1960, I can find no IC triple hoppers. The
IC 713000-713749, built 1929 by GACC and Standard Steel.
Renumbered to 81000-81744 in 1951.
Three cars converted from 81000-series into woodchip hoppers with raised sides and roof, numbered 81750-81752 in 1951.
C&IW 1000-1099, built 1929 by GACC. 35 cars renumbered to 900-934 in 1951, others leased to C&IM under original numbers (but in C&IM paint).
IC 81790-81799, built for People's Gas in 1947, sold to IC in 1957.
Since I don't have any triple hoppers in my car fleet I can't measure and compare any of these cars against the models in question. If anyone wants copies of these car diagrams, email me offlist!