Update
On further enquiries, I am advised that the door is from "an Antonov" of unspecified type. Given that the door came from Brisbane Airport, one would have to imagine that it could have come only from an An-12 as several of these have been based here over the years whilst no other Russian types have been resident. The door has insufficient curvature to be an external door so it is most likely a cockpit door. The paint scheme suggests that it's an external door but apparently it's not unusual for An-12 interiors to be painted in two colours with a black cheatline. However, An-12 cockpit doors are rounded at the bottom whereas this one is straight. It has been suggested that it does conform to the shape of an An-2 (Two) cockpit door but we don't see many of them in BNE and it's probably too heavy anyway. The unusual pattern of portholes is unlike anything else I've seen. In addition to the 4 portholes which are clearly visible, there could be another 6 which appear to have been "bogged over".
While we continue to look for any identifying marks, I think the best line to follow is to try to find such a door on an An-12. Thanks everyone for your input.
Rgds