INTERPHONE BC-335 "jack box"

Here's yet another of my 'little electrissical boxes' collection. I honestly don't have the slightest idea where/when I got it, and until just now (with a quick Google search before this showing) I've always sorta guessed it was some orphaned part of a public address/'hearing assistance' sound system -- turns out that instead, it was apparently part of some kind of aircraft/radio communications setup. Go figure?! :-)

http://aafradio.org/flightdeck/BC-213.htm

Otherwise it is a small but very nicely made little aluminum box, now containing nothing more than a (actually quite unique and very nicely made as I look closer at it) rheostat -- the "jacks" it once also held are now gone. I don't *think* I'm guilty of doing that to it...??