I'll put this out there to any readers passing by. At the Huia Settlers Museum, there is a case with heaps of items picked up from the Manukau Harbour coastline over the years, from Onehunga to Whatipu. Included is the above -- what looks like a three-funnel liner, with radio mast (?), and underneath "TRADE MARK REGISTERED".
Any help pin-pointing what this might be from or to do with, just out of interest, would be appreciated.