These trucks were used under the semi-streamlined baggage cars built by the Santa Fe in their Topeka shop from "kits" made by Pullmann-Standard. The first batch of 50 cars (3700-3749) was built in 1956 and were 64' in length. Another batch of cars of the same length followed in 1958 (3750-3799). Over the next 6 years, another 140 cars were added to the roster (3800-3939) and although technically identical, these were slightly longer (74').
An N scale version of this truck is available on Shapeways (designed by TechnicalATSF) -
Said truck is correct for the ATSF baggage car kit sold by Skytop Models -