Police are appealing for any information on the thief who stole the pounamu and gold key to Wellington City, after its anonymous return.
The key was handed into the police yesterday by a lawyer on another person's behalf and given to Wellington Mayor Celia Wade-Brown today.
Wellington Area Commander Chris Scahill said, despite the quick recovery, police still viewed the theft with great importance.
"The key is obviously a significant item for the city and so therefore it's a significant theft. We'll take every avenue that we can to bring that to a conclusion."
The 110-year-old key, which is valued at $8500 and was gifted to the city by a jeweller in 1904, was stolen on 14 September.
Wellington Museums Trust director Pat Stuart said the museum's immediate response was to check security and police have also reviewed it and found it robust. But she said changes would be made, in particular upgrading the cameras.
Ms Stuart said she was delighted the key was back where it belonged.