I didn't have the chance to look into empty hoppers until the late
60s, but many cars from that era interiors were unpainted.
Up here in the frozen tundra the coal (contents) freezes in the
cars. Removal is buy whatever means is available. Sometimes torches
are places against the hoppers to thaw the coal (contents). At a
mininum this burns the paint off the hoppers leaving them with
grayish, yellowish, orangeish colored hoppers.
I was told it once took 4 men 6 days to unload a car of iron ore.
Mason City Iowa