MILW had an unique assortment of rollingstock with their horizontal-ribbed 40’ boxcars and cabooses. Can MILW’s horizontal-ribbed steel cars be considered exterior post? Exterior post started to became mainstream on boxcars for most railroads in the 1960s, though ribs on most 1960s and newer exterior post rollingstock are vertical.
No, they had internal bracing like a normal box car. The ‘rib’ sheathing allow the use of lighter sheet metal(weight savings).
Jim