The CC-5 might possibly mean Continental Can Company plant number 5. If it was a can produced in 1917 they might have used just the CC back then rather than the usual CCC that you see on later cans. The can manufacturing company does goes back to 1904 though I have not seen any early cans to verify the CC usage. As far as I am aware of Continental Can had no connection to Continental Oil except for maybe supplying some their containers. Cheers, Don.