The stamp is one of four created during 2020, to mark this important period in Irish history.
Speaking about the iconic painting Michael Waldron, assistant curator of collections at Crawford Art Gallery, says the work resonates significantly with Crawford visitors.
"Seán Keating'sspeaks so much to the Ireland of a century ago.
"It combines hope and tense determination, as well as national and local history.
"As much as it is about the actions of the War of Independence, it also seems to contain a symbolic reference to the virtue of waiting and withholding fire.
"It was purchased from the artist in 1924 through the gallery's Gibson Bequest Fund, and has since become a go-to painting for visitors, and particularly the descendants of those depicted."
Each of the figures in Keating’s painting is a portrait made in 1921 by the artist during a truce in the Irish War of Independence.
Depicted are members of the North Cork Brigade of the Irish Republican Army: Jim Riordan, Denis O'Mullane, Jim Cashman, John Jones, Roger Kiely, and Dan Browne.
Shown in profile, as figures from an Ancient Greek frieze,presents six men in a heroic light.
Having invited these men to his Dublin studio, Keating would later say:
"They trooped in, dressed and armed very much as they must have been on many an ambush."
Much of Keating’s work at this time documented the changes witnessed during the Irish War of Independence, and the Civil War, which followed.
These paintings were populated with proud and defiant men and women.
has resonated with many over the years, reimagined by the Fair Hill Men's Art Group and featuring as the cover image for the best-selling .
Crawford Art Gallery will host two significant exhibitions later in the year directly supported by the Department of Culture, Heritage and The Gaeltacht focusing on the commemorations.
Commenting on the news that Keating's painting was chosen by An Post to feature on a commemorative stamp, Mary McCarthy, director of Crawford Art Gallery, is encouraging members of the public to come and view the original artwork.
"We are thrilled to have Keating’s iconicrecognised as a key image with An Post, thereby increasing its visual recognition and circulation.
"Meanwhile, we invite all to come see the original in Crawford where it’s on display as part of Mise Éire," she said.
is currently on display at Crawford Art Gallery as part of the free exhibition Mise Éire, and throughout the year.