For those that are interested, I think you have the right object PP in that photo of Marquis de Rays. A mate of mine that was born in Kavieng sent me some info about it. Some links below.
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Its a Milling Stone (flour). The story is that it was first taken to Kavieng (where I was born) by a guy called Marquis de Rays.
I was told by a friend in Kavieng who was related to famous local German "Queen Emma Forsayth", she ran Rabaul
and her home was up on the hill just near the drom, ...that she took it over to Rabaul, for some dumb reason.
There was also another story in Kavieng that this was one of two wheels dropped off by either;
William Dampier or Abel Tasman
I can not remember who/who did the trick or if this was a true story....
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The wheel is very large. It looks that way but its the same wheel.
That wheel was set up near Admiral Yamamoto HQ, just over the road from the Cosmopolitan Hotel (The Cosmo),
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Anoughter later view of the bunker complex:
In your fathers image that's one of the bunker heads in the background, the hotel was just next to this.
This is another view of the complex;
http://www.nla.gov.au/apps/cdview?pi=nla.pic-an22703914