The Dalman two-level truck design used additional springs to provide a smoother ride. With ASF as the main supplier, many freight cars built in the 1920s were equipped with Dalman trucks. Railroads using this two-level design included Chesapeake and Ohio, Chicago Great Western, Illinois Terminal, L&N, Milwaukee Road, M-K-T, Nashville Chattanooga and St.Louis, Pere Marquette, and many Texaco 10,000 gallon tank cars.
Dalman two-level trucks could also be equipped with a Barber Lateral Motion Device. This feature employed steel rollers and a roller seat between the springs and bolster; allowing a little side-to-side movement of the carbody (and thus reducing wear to wheel flanges, journals and couplers). Railroads using these trucks included ATSF, Canadian National, Canadian Pacific, Central of New Jersey, CB&Q, CNW, Illinois Central, MILW, Missouri Pacific (and subsidiaries I-GN and StLB&M), Northern Pacific, Rock Island and Southern Pacific.
Many of these trucks were used under 40' and 50' auto boxes into the 1930s (at which point ARA/AAR trucks became more popular). Circa 1947, Illinois Terminal purchased 40' AAR boxcars using two-level trucks (the last known use under new cars). Circa 1956, ATSF replaced the National B-1 trucks under their 50' steel reefers with Dalman two-level trucks salvaged from retired auto boxes. Although never officially banned from interchange, Dalman trucks eventually vanished from the rails as their cars were either retired from service or retrofit with newer truck designs. As such, it's unlikely that many (if any) of these trucks were still in use by the 1970s.
Micro-Trains makes the only N scale Dalman truck (equipped with "Lateral Motion Device") -
Micro-Trains - wheelbase 10.6mm, frame width 15.56mm, wheel size 33", axle length 13.75mm