The Barber Lateral Motion device used steel rollers and a roller seat between the bolster and springs to provide a little side-to-side movement of the car body to the track, resulting in a smoother ride. U-section trucks with this feature were manufactured from the early 1920s to the late 1930s. Railroads that used this style of truck included ATSF, B&O, CB&Q, CN, CP, CV, CofG, C&NW, C&EI, ERIE, DL&W, GTW, IC, MP, NP, RI, SL-SF, SP, T&NO, T&P, UP, and WP, also PFE and SFRD.
Below is a link for the data sheet about this truck.
TMW-109 / TMW-209 Data Sheet