Following Irish independence in 1922, existing British pillar boxes were retained, and when the Irish Free State left the Commonwealth following the declaration of the Republic of Ireland in 1949 existing pillar and wall boxes were then painted green.
Many of these are extant around the country, retaining the monogram of the monarch who reigned at the time of the box's installation. The Department of Posts and Telegraphs continued installing similar pillar boxes and wall boxes, but with the initials SÉ (for Saorstát Éireann), a harp or the P & T logo, instead of a monarch's monogram. Since 1984 An Post, the current Irish postal administration, use the An Post logo to adorn their posting boxes.
After I published this post I received a message from a follower indicating that this letterbox was a King George edition but that the door must have been replaced and as a result I decided to review my catalogue of photographs and eventually located a photograph of a letter box in Cork City that supports his suggestion. The Image and description is included below.
Post Box Wall Type G V R by W&T Allen London [11 Morrisons Quay In Cork]
I do not remember seeing this type of letter box before so i assume that there are not many remaining.
Described as an early twentieth-century cast-iron wall-mounted post box with raised G.R. insignia, set into the façade of 11 Morrison's Quay.
"In accordance with the decision of Cork City Council on the 28th day of May 2007, the following structures were added to the Record of Protected Structures included in the Cork City Development Plan 2004." The letter box in my photograph is one of the structures added to the list.
GR was used in the the British Isles [what is now the UK and Ireland] during the reign of George V [1910 - 1936].