Back in the 1960's and 1970's Kodak (here in the UK) had a factory service for colour processing (Kodachrome by mail, and Ektachrome and Kodacolor through dealers). As most films would be sent back to them in the cans, I wonder if Kodak re-used them for packing new films; it would seem wasteful to have thrown them out ? .
Certainly the UK film Gratispool, who sold and processed Dynachrome and other films back in the 1960's, re-used cassettes and tins to pack their own-brand films, with labels over the old printing.....I have an ancient "Gratispool Colour Film", which is their own brand (presumably Dynachrome), packed in an re-used Ektachrome cassette !