Union Pacific O.S.L. Cattle Car

I just purchased some HO scale trains, which included a UP cattle car. On the side, it says, “Union Pacific O.S.L.” I’m curious as to the meaning of O.S.L. If I had to make a guess, I’d say that the L stands for livestock, but I really have no clue. Does anyone know what this means?

Actually, OSL was the Oregon Short Line, a subsidiary of the UP. I recall seeing a number of UP freight cars (back in the 1960s) with OSL sublettering, and others with “OWR&N” (Oregon-Washington Railway & Navigation Co.) sublettering. My information says they were merged into the UP in 1936.

Thanks very much for the information! It’s good to know!