His girlfriend Danielle Oylear was in the car with him at the time of the accident, and was forced to grab the steering wheel and lift his foot off the accelerator to bring the car to a stop.
Analysis of parts of the vehicle in February revealed the object was made of, or contained, fragments of stainless steel of a common grade used in vehicle parts and other everyday items such as tools and cookware, police said.
The object also comprised common minerals naturally occurring in soil or dirt in the South Island.
In February, Detective Senior Sergeant Malcolm Inglis said the case remained open and if any new information came to hand it would be investigated further.
"Our thoughts are with the family and friends of Rutger Hale as we are at this stage unfortunately unable to progress the case to any satisfactory conclusion."