South Australian MLE's

I have come into posession of an MLE that has "south australia" stamped into the butt socket and "SA" on the reciever. The MLE barrel is knackered, but it has lithgow markings on it and a non matching serial number on it - at least i think it does, i cant tell much about it as i was looking at it with a pen torch. It doesn't have a bolt, the previous owner thinks he knows where it is but reckons he hasn't seen it for 25 years

Does anyone have info on or know about MLE's in Aus?