Late last year, Martin McCrae, the Scottish great-great-nephew of Dean, wrote to the Winton Community Board saying he would commission a headstone for her unmarked grave.
But someone beat him to it.
On assignment in the Central Southland town to take photographs of the site, Otago Daily Times photographer Gerard O'Brien discovered a mysterious headstone was erected on the plot where locals say the grass never grows.
The headstone read - "Minnie Dean is part of Winton's history where she now lies is now no mystery".
Informed of the mysterious headstone, the Dunedin-based author of Minnie Dean: Her Life and Crimes, Dr Lynley Hood, said she was "gobsmacked" by the news.
"[This] is another example that Minnie Dean just won't lie down."
Mr McCrae said he was disappointed to hear of the site being marked without the consent of family.
"As far as we are concerned, our aim is to put a memorial in place that can provide some closure and healing for the family.
"We have sought this all along."
Closure came for the family in February in the form of a memorial service and the unveiling of a new headstone to replace the unauthorised stone.
While the service provided closure for the family, mystery remains over who installed the headstone and the wooden sign pointing to its whereabouts.
Winton Community Board chairman and local publican John McHugh said he was in possession of the granite slab but no-one had claimed ownership.
Mr McHugh said he had no idea who placed the headstone on the site, or what their reasons were.
"It is a complete mystery."
He had been informed that no monumental masons in Otago and Southland made the headstone, but it had been made by a professional.
More than a century since she was found guilty of infanticide and hanged, an increasing number of people were flocking to see her grave, Mr McHugh said.
