yes ive seen the photos but i cannot find any type of mine that looks like this
also there are no fittings for the contact horns
heres a similar one,no id though
https://www.dreamstime.com/big-naval-mine-explosive-device-wwii-naval-mine-image172910944
Pretty sure there was a line of these in the entrance to Wellington Harbour back in the day, maybe to keep the impending Russian invasion out (yes, it was a real perceived threat in NZ in the late 1800s). There was an mine station just along the shore from Fort Ballance.