I took photos of this car back in 1984, when it was still a tool shed in the Sierra RR´s Oakdale yard. In much better shape then.. Your photo clearly shows that the boxcar body was a later addition to one of the original YSL 18ft flat cars.
Lennart, lwhen I first saw this boxcar it was still being used in a farmer's field for storage. When I went looking for it again to photograph it I learned it had been moved to the Sierra Railroad yards.