They definitely had some black Overnight Merchandise Service box cars, used between Los Angeles and the Bay Area. However, all photos I have seen only had an SP herald of the same type seen on other Espee box cars - not this elaborate large design.
Although I grew up in Southern California in the 1950's, I never did actually see one, even though I watched a lot of Southern Pacific trains on the Sunset Route, which goes east from Los Angeles. The route for the black cars was to the north, and at night. I never did get out to watch trains on the "other side" of the Espee until I started driving, in 1962, and still, at that date, never saw a real SP black merchandise car.
