[Arran]

A type 84 rectifier is basically the same as a 6X5 with an older style six pin rather then an octal base, but since 84s are not particularly hard to find I would ditch the adapter and use an 84. Why the adapter was used one can only speculate, both during WW2 and the Korean war there were sometimes shortages of replacement tubes but it could have happened at any point since the set was built. the two wires cut and twisted together may have been an improvised capacitor called a gimmick. I really think you should start a new thread with any questions you have as this one is long enough.
Regards
Arran