Lucky you, I lived in an old building ( built 1939) and I had a few of the original 5A socket outlets there. Did a replace though, as the wiring at least was from the 1970's and was rated for 16A socket outlets, and the fuse box had been replaced with a more modern version with a RCD device. At least I did not have to pull new cables and earth wiring through the steel conduit, which is a pain in older buildings, as they all had 3 wires. Some flats still have the wiring from that time, complete with crumbly gutta percha DCC rubber wire, which tends to shed insulation almost by looking too hard at it. I really dislike that stuff, at least the 1960's 70's PVC only sheds PCB oil in the green goo, and does not go bang in the night and weld into the conduits.
Worse is the cheapskates who only replace the active conductor and not the neutral, to keep cost down yet have a working RCD, and you have to work on that polished bovine deposit later.