I had to laugh when I saw this topic.
I had been emailing with Joe Tedesco and mentioned I installed a 3R panel outside on a Friday and it had graffiti on it by Monday morning.
Joe sent me an email back with a link to here.
For my particular case no NEC violations, the panel has absolutely no markings on the outside.
Luckily you need a key to open the door and see the nameplates.
The GC has since cleaned the graffiti and I imagine the panel will be painted to match the building finish. (at least till the next tagging)
Bob