In 1929, the Southern Pacific constructed 65 mill gondolas at the Sacramento Shops. The cars had an inside length of forty-eight feet, straight side sills, fishbelly center sill

underframes, Dreadnaught drop ends, wood floors, drop-shaft staff hand brakes and Symington ARA cast sideframe trucks. The cars were assigned to Class G-50-13 and numbers SP 93900-93949 and Pacific Electric 25000-25014. In 1930, and additional 100 cars were built by Ralston Steel Car Company. These cars were essentially identical, the major visible differ- ences being slightly different castings on the end sills around the draft gear and Dalman two-level trucks.

In June, 1951, the 15 PE cars were transferred to the SP and assigned to numbers 94050–94064, in order. All were renumbered by June 1, 1952. In 1956, the cars were renum- bered again, this time all 165, to the series 310000-310164. In 1960, 154 cars were still in service. By 1965, the number had decreased to 52 and only one car remained in revenue service in 1970.

Includes two of the artwork shown.