About 8.45pm (Friday 30 September 2011), a man entered a betting agency on Amy Street, Regents Park.
Armed with a hand gun, the man approached the front counter and demanded cash.
A male staff member handed an amount of cash to the man, who then fled the premises on foot. He was last seen running west along Amy Street.
Officers from Flemington Local Area Command and the Forensic Armed Robbery Unit attended. They established a crime scene, which has been forensically examined.
They have also examined CCTV footage provided by the agency.
Detectives now wish to speak with a man who they believe can assist with their inquiries.
He is described as being of Pacific Islander/Maori or Asian appearance, 160 to 170cm tall, and with a large build.
At the time of the robbery, he was wearing a long-sleeved T-shirt, black pants, white shoes, a black jumper and black gloves.