The prototype is discussed in the Rolling Stock Reference Series – Volume Seven, Santa Fe Open-Top Cars, pages 236, 248-249. In 1948 the Santa Fe received 200 AAR standard triple hoppers from AC&F. They ran on ASF A-3 trucks and had Ajax hand brakes and Royal F brake adjusters. They were followed in 1949 by 500 identical GA-77 hoppers from Pullman-Standard. Virtually identical were the 500 P-S built GA-81 in 1951, the 500 GA-86 in 1953, the 900 GA-100 and 200 GA-109 in 1958.
The Stewart model is a basic model with cast on grabs and minimal break rigging. The brake wheel is generic; there are no slope sheet supports, and the inside lack detail. The three foot rule applies here as well, but it is a good representation of a Santa Fe Offset triple hopper. It weighs 3.45 oz as compared to the 3.8 oz NMRA standard. Stewart is no longer in business, but Bowser acquired the tooling.
Thanks to Steve Sandifer for the review and photos.