> It appears to be canvas with black coating or paint
Given the probable age of that, it could be *actual* rubber. Rubber coated cloth was widely used for water proof articles, raincoats etc. When it degrades it isn't very strong, and oil degrades it even faster, I dunno what would be safe to use on that roll of that is the case.,if it is paint, it's worse...
I don't think the folks who designed cloth tool rolls ever thought about how anyone was supposed to clean the silly things...
Most of the staining is likely rust, which won't easily wash out....
Very kewl set tho, hardly ever see such a complete set of tools together like that, the rod with the notch in the end is interesting (carb tool?) hmm