It was stolen at around 3.30pm on Friday May 25, from a car parked at Heworth Golf Club on Muncastergate in York.
The ring, valued at around £12,000, was in a bag of golf clubs which had been left in the back of a Jeep Grand Cherokee. The bag was recovered a short time later but the ring was missing.
A 17-year-old local youth has been arrested in connection with the theft. He has been released on bail to allow for further enquiries.
PC Peter Smith, of York Safer Neighbourhood Team, said: "The stolen ring is so unusual that anyone who sees it will instantly recognise it.
"If you have seen this ring and can help to return it to its rightful owner, I urge you to contact the police or Crimestoppers straight away."