That's interesting. I suspect I need to look at the chute with my magnifying glasses on. It certainly doesn't appear to be made up of an outer skin with an inner cast lining.
The milk car chute itself is a single cast piece, with a sheet metal cover. There is no skin and lining. At least this is true for every 027 milk car I've handled, and its been quite a few.
There is a sheet metal part (#3472-25 can sweep arm) attached to the bottom end of the chute.
See the attached PDF below.