The object that killed an Otago man while driving near Wanaka 15 months ago will continue to be a mystery.
Rutger Hale, 22, was driving with his partner when an unidentified object punctured the windscreen and fatally struck him in the head in October 2013.
The object has not been found, despite extensive searching and forensic testing.
Christchurch coroner Richard McElrea has released his findings into Mr Hale's death and said it was unlikely the object would ever be fully identified unless significant new evidence was given to police.
Mr McElrea said the object was likely to have been manufactured and contain stainless steel.
"The finding at post-mortem of a semi-circular wound about 80 millimetres in diameter indicates the object had a circular or at least semi-circular profile and a degree of roughness," Mr McElrea said.
'It was moving very fast'
It was a dark and rainy morning when Mr Hale was driving with his partner along the Lake Hawea-Albert Town Road.
When his Subaru Legacy went past the Te Awa Road intersection, another vehicle came around the corner at the top of the hill.
The coroner said as the vehicles drew level with each other, an object smashed through the front windscreen and hit Mr Hale on the head, before crashing out through the back window.
His partner, Danielle Oylear, who was unharmed, tried to stop the car and it eventually came to a halt in a ditch on the other side of the road.
When emergency services arrived, Mr Hale was already dead.
Coroner McElrea said Mr Hale had a penetrating wound to the right side of his face and head.
He believes the speed between the two vehicles was in the range of 160 km/hr, and Mr Hale and Ms Oylear would have had about a second to see the object.
During the inquest, Ms Oylear described the object to the coroner as being "the size of a tissue box or brick" and beige in colour.
"My instant thought was somebody threw something but I would have seen an arm or a window down or seen a person," she said.
"I'm pretty sure the window was up. It was moving very fast."
The coroner said it was likely the object slid off the deck of a white oncoming utility vehicle. Police have not been able to identify the driver.
The coroner made no recommendations.