Operating Era: 1910-1956. THIS SERIES OF KITS NOW COMES WITH OUR NEW ONE-PIECE ROOF FRAME. Southern Pacific, Union Pacific, Chicago & Alton. In its evolution of standard house cars the Harriman Lines progresses from 36' fishbelly side sill cars to 40' length and then increased the height. By 1910 they had the B-50-5 as their standard house for box cars and the R-30-4 for reefers. The reefers had switched to the Bettendorf single I-beam center sill with success. The switch for the box cars resulted in the B-50-6. The first deliveries were taken in 1910, before the Safety Appliances Act and so had no ladder grabs on the ends or steps at the left corners of the sides or roof end walks. Deliveries of 1911-2 remedied the situation and the early cars were improved to match in the 'teens. 1913 deliveries varied according to the road. The house portion was revised to remove the lower lumber door on the end and the lower brace on the door. UP cars retained the same underframe as earlier. SP cars received a 6" deeper I-beam floor, resulting in a new class, B-50-9. C&A cars delivered that year were also -9 but differed in having no end doors.