This truck was manufactured by the Buckeye Steel Castings Company from the late 1920s until the late 1940s. Conventional trucks, such as this one, complied with American Railway Association standards, and prototype features included a spring plank spanning across both side frames and, in each side frame, four coil springs grouped close together. Field research was conducted at the Niles Canyon Railway at Sunol, California.
Below is a link for the data sheet about this truck.
TMW-106 / TMW-206 Data Sheet