is this a 4 pins or 6 pins connector at the end (xlr type)? if so, maybe you could compare wit some Clear-Com headset and unit?

those bellow are much recent...
http://www.clearcom.com/Products/par.../headsets.html

in the past i repaired tons of white and green model.. but none had the circuit you discribe so far. everything was done with the beltpack.

Is there any model # or company name written on?

For sure you must have a base station somewhere to do some tests. So just probe it to get the Headphone outputs wire, mic, and probably you'll discover a Vdd line as well.