Box cars in the past fifty years have generally fallen into one of five distinct frame lengths, 40-, 50-, 52-, 60- and 86-foot. The least common of these is the 52-foot box cars. Although not as numerous as its shorter and longer companions, the 52-foot non-insulated box designs have provided an important role in the lumber industry.
The car is essentially a “stretched” 5277 with one-foot added outside the bolsters giving the car its distinctive overhang. It is equipped with double sliding doors and a cushioned underframe. Southern Pacific was the sole original operator of this design and ordered 700 of these unique looking boxcars split between Southern Pacific (525 cars), Amador Central (75 cars) and the Longview, Portland & Northern (100 cars).