"It's not polished like classical Polynesian and Maori artefacts that you see. This is just a roughly fashioned, purely utilitarian adze."
Its tip had been broken off, which may have been why it was rejected. Mr Neilson, a kaumatua of South Taranaki tribe Nga Rauru, said the adze would have been made for carving wood.
"Our eponymous ancestor [Rauru] was the originator of wood carving."
It's made of a very hard black stone, possibly chert. Similar stones do wash up on the Wanganui coastline.
Mr Neilson said the tool could have been made thousands of years ago, and Maori whakapapa went back through hundreds of generations in New Zealand.
"It actually endorses the Maori tradition that we've been here a lot longer than the 600 to 700 years that anthropologists and historians talk about."
He plans to keep the adze because it was found within his tribe's rohe (boundary) rather than hand it to a museum.
"It's time we stopped doing that and looked after our own taonga."
He'd like to make it part of a small collection of taonga held by his Nga Ariki hapu at Waipapa Marae in the Waitotara Valley.
On the subject of his ongoing dialogue in the pages of the Chronicle, Mr Neilson said he would keep it up.
"I get a bit tired of it but my people tell me to carry on."