Operating Era: 1934-1964. Union Pacific. During the Great Depression most railroads converted their fleets of auto cars to box cars by sealing or removing one door. Union Pacific began such a conversion in 1934 using 500 A-50-6 auto cars, creating the B-50-20 class. The were lettered in the Roman style. Another 386 cars were converted in 1940, lettered in white Gothic. Yellow Gothic was used from 1947-1966. AB brakes were applied in the 1950`s. The cars lasted to 1964. Kits 5900/01 have K brakes to model the early years while kit 5951 has AB`s for the later years. Both yellow and white decals are included to cover the life of the car.