[Lugers down under]

Yes,
The extractor does have "Geladen" on both side, The grips have GS stamped inside.
I share the same view that it was most likely built up from spare (un-numbered) parts in one of the arsenals. There were a number of New Zealanders as part of the relief force in the indies after the surrender by Japan. I think that Dr Ongly was attached to the NZ forces.

I also think it is an interesting piece and seeing the original Vickers contract guns were built from spare parts (DWM) to all intents and purposes it is a Vickers gun and "one of a kind."

What is also interesting is the lack of numbers and acceptance marks especially on the frame , receiver and toggle. I can accept no numbers on the barrel (the arsenal did had spare un-numbered barrels)

I would be interested in your views

Regards
Murray.