Robbers threatened a Middleton householder with a gun but left empty handed after he refused to answer the door.
At about 7.40pm on Wednesday 13 March 2013, the trio knocked on the door of the house on Dean Walk.
The victim was upstairs and asked what they wanted from him. One of the men then pointed a gun at him, called himself Jimmy and demanded the man open the door and hand over cash.
The man refused to open the door and the offenders left.
The offender carrying the gun is described as being white, 5ft 8in tall, of stocky build and in his mid 20s to early 30s.
The other two men were white and also in their mid 20s to early 30s. One man was wearing a white face mask.
Detective Constable Nick Price said: "The victim may not have been willing to entertain these men, but what they did is being treated as a serious offence all the same.
"This was an attempted armed robbery where the offenders made threats, pointed a gun at their victim and made demands for cash; they fully intended to make the victim feel as though he was in danger.
"These dangerous offenders therefore need to be caught.
"We would urge any witnesses to come forward."
Anyone with information is asked to call police on 0161 856 1706 or call the independent charity Crimestoppers anonymously on 0800 555 111.