Browsing through some TGL documents I noticed, that the governmental construction in the German Democratic Republic used ring circuits in all apartments. 10A ring, wired with 2,5mm2 aluminum. Usually 2x2,5mm2, grounding achieved by installing a jumper wire between neutral and ground at every receptacle/light fixture.. After 1984 mandatory RCD protection for kitchens and bathrooms-> 3x2,5mm2 aluminum.