Transit Crime Investigation Unit detectives are investigating following threats made at a Melbourne railway station in March, Victoria Police say.
Investigators have been told the victim, a 59-year-old Beaconsfield man, was standing on Platform 5 of the Flinders Street station when approached by an unknown man about 9am on Tuesday 28 March.
The man produced a folded knife and threatened the victim before walking off towards Flinders Street, near Elizabeth Street.
The victim was not injured during the incident.
Detectives have released images of a man who they believe may be able to assist with their enquiries.
The man is described as being aged in his 30s, about 170cm tall, with a medium build and short black hair.
He was wearing a shiny white shirt, orange and grey jacket and was carrying a black backpack laptop or tablet with distinctive stickers on it.
Anyone with information is urged to contact Crime Stoppers.