Police are investigating a theft at a jewellery store in the city last month.
A man attended the Collins Street business about 12.30pm on 16 March via an appointment he had made to purchase a diamond.
Whilst looking at the diamond it is alleged the man swapped it with a fake.
Investigators have released images of the man who is described as being aged in his 30’s with a medium build and a bald head.
He was wearing glasses, black jumper, blue jeans, black runners and was carrying a black backpack.
Anyone with any information about the theft is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au