Published Wednesday, 03 October 2012
The robbery left the postmaster badly shaken. (© Getty)
Two armed robbers entered the branch in the village of Culmore on 9 July, threatening the postmaster with a gun, before escaping with what is believed to have been a substantial amount of cash.
The robbers then abandoned a stolen taxi vehicle and made their way across the border on foot to Muff in Co Donegal.
Crimestoppers UK and the Post Office is offering the reward for any information that leads to the arrest and conviction of the persons responsible for this crime.
Susan Brew, Crimestoppers UK manager for Northern Ireland, said: "This was a heinous crime that has seen an individual simply doing his day-to-day job threatened and left badly shaken.
"This has rocked a close community and I am urging anyone with information on this incident to contact Crimestoppers UK anonymously.
"We only want to know what you know, not who you are."
Mark Gibson, of Post Office, said that those who run the Post Office branches provide important services to local communities.
"Any robbery or attempted robbery is not only traumatic for those involved, but is also an attack on the local community.
Crimestoppers telephone: 0800 555 111
"Post Office Ltd is supporting Crimestoppers in their efforts to apprehend those responsible and would urge anyone with information to come forward as soon as possible."