"Coil-Elliptic" trucks added leaf springs to provide a smoother ride. Double Truss trucks with this spring package were manufactured from the early 1930s to the late 1940s. Railroads that used these trucks on some cars included BAR, C&O, CGW, D&M, DT&I, Erie, LNE, LS&I, MRS, N&W, NP, TA&G, VGN and WM, and some AC&F tanks cars built in 1937. A similar 70-ton version was used by B&M, CNJ, CRP, D&H, DT&I, Erie, LNE, MEC and PRR.
Below is a link for the data sheet about this truck.
TMW-108 / TMW-208 Data Sheet