The numbers definitely remind me of those found on the network sockets at my University.
Sven, maybe all you need is a screwdriver. Most European plugs I've wired allow for quite some slack inside, so you can just open the cord grip screws, push the cord back in and retighten them. Though I'd also have a thorough check on the terminal screws, maybe the connections have gotten loose from the strain, and if that thing wasn't installed properly right from the beginning the connections are probably none the better than the strain relief.
BTW, it pretty much looks like a fancy design plug, and those can be pretty flimsy in some instances.
The marks on the cord look like it has once been under the strain relief but has gotten loose. I'd guess loose screws and nice strong pulls on the cord.
