16" Wide 5 drum replacement

[411Ton]

in prep for Hershey this week, I retook some photos of the rear wide 5 drum/hub assy. I didn't realize that the two sides were different. Does anyone know which one is original? On the smooth one (without the ribs) I took a pic of stampings. My AI research seems to indicate that the stamped one is a replacement, although I'm not certain of this. I also saw a post in this string that said that the ribs were on passenger cars? The front and rear are both 12" diameter with 2" face.