It's fine without the film. There's a protective paint layer on the surface of the copper door. If the paint is gone, you can buy spray paint to paint it. But the color of spray paint should be similar to that of the copper door. Or you can contact the manufacturers and ask them to repair it.
There are several maintaining methods: 1. Keep the copper door, especially its surface intact and prevent bumps and scratches. If accidentally the surface of copper door is scratched, use colorless paint or wax to fix it as soon as possible to prevent the scratched area from oxidizing. 2. Frequently clean the copper door by wiping the dirt to keep it clean. 3. Regularly or irregularly wax the surface of the copper door: Using dry cotton towel to wipe off the dust on the copper door and waxing its surface. 4. If things like greasy dirt remain on the doors and windows, washing them with neutral cleanser. Though copper door is naturally resistant to corrosion, chemical changes will easily happen when it meets a large number of sulphur and sulphides. 5. Mind the strength when open and close the door. The strength should be even. The door itself is not easy to be damaged, but some of the mechanical parts of it may be abraded or less flexible in the process of using. Therefore, it's necessary not to open or close the door with much strength. The inflexible part can be fixed with a small amount of lubricating oil. Do NOT use too much. Then use cotton cloth to wipe off the oil to avoid dust.
It may be easy to rust and generate verdigris when it is exposed to the rain. It will affect the appearance and usability. My suggestion is to recoat a film.
