After having a quick browse through my copy of "Chainsaws: A History", it looks similar, but not identical, to a picture of the Teles Smith saws pictured on p. 60-61 and 209. It also bears some resemblance to some old Danarms, but since Teles Smith made saws for the British Army, the chances of them ending up in Australia would be much higher, I would think.
Most of the old 2-mans I've seen like that had fuel tanks set 90° to the bar, so that narrows the field down significantly.
I wanted to look up those saws on Acres' site, but it seems to be down. Hopefully not a victim of all the flooding down Vancouver way. For what it's worth, I couldn't really find any information at all on those Teles Smith saws, and to be honest I'd never heard of them before I read that book.