Eugene Dvurechenski <jno@glas.net> says:

    there is "su" top level domain still maintained in ex-USSR.  at
    least "*.msk.su" zone (Moscow, USSR) is still in use.

Tools/world/world

@@ -291,6 +291,7 @@ nameorgs = {
     #
     # See <url:http://www.ripe.net/docs/ripe-159.html#222123>
     "uk": "United Kingdom (common practice)",
+    "su": "Soviet Union (still in limited use)",
     }