1. rust (after 9 months)
2. You are sharp, thus scratching the paint under the license plate. Gummiabtandhalter for example would have been a solution
3. I sell my car now and am now faced with the problem abzukriegen my plate again and affix the number plates temporarily.
All 3 problems could be solved. 1st through better quality, 2. by rubber spacer and 3rd by a different principle, for example, license plate insertion.
On my new car I'm going to use plain black plastic holder.