Without looking at the the circuit boards properly most of this is guesswork, but educated guesswork
Judging by the makeup of the box and the way it is generally put together I would say it is homemade, and from the duplication of components I wouldn't imagine that it is just a transfer from another housing I think it has been made up from other items.
It appears to have several audio inputs (you say it's from an "audio guy") and there are several pots (variable resistors) which appear to control the input signal, along with (if I'm seeing it right) a VERY large capacitor (the silver can type object) which is either used to stabilise the voltage or to give a huge boost when required.
I can't see it being from a telephone exchange, despite the variable inputs.
It looks as though it's taking a fixed signal from a single input and then using the jack pugs in a variety of sockets to allow for different "effects" to be applied to the signal, either to enhance it, amplify it within a certain range or to control the effects within a fixed parameter.
Without seeing it properly I don't know, I'm just working on what it looks like, without seeing the circuits properly though it is just guesswork (unless somebody else recognises it as the guidance system from one of the ferries