Hi everyone, I just got a set of Lackawanna Phoebe Snow smooth-side passenger cars. The roofs on these cars are ribbed or grooved from front to back. I also have a set of Milwaukee Road smooth-side passenger cars and their roofs are smooth. Were the ribbed roofs indigenous to the Lackawanna or did other railroads have them also?
Speaking of ribs, were there ribbed-sided and smooth-sided passenger cars also? If so, what was the significance or reasoning for the two types and was there an official name for them?