That's interesting thought Patrick. Who checks the proof marks in Germany? And when? Good job it's not the job of the Police here. Some of them can't even see the time let alone a proof mark!
I recall a time when we alllowed a group of civilians to shoot a few weapons - a GPMG, MG42, Steyr AUG and SA80 plus some others and when checking the legal niceties of it all, one of the local gun cops told me that we'd have to have them all commercial proofed if civvies were shooting them! I just put on a well practiced befuddled look, rolled my eyes skywards and just got on with the task in the usual way - properly! Mind you, I did cross his name off the list as well! You can't be too careful can you?