A 90-year-old letter written by Michael Collins to Thomas Ashe is expected to fetch around €50,000 at an auction tonight.
The letter is accompanied by a portrait of Ashe, the 1916 Rising leader who later died on hunger strike, by the renowned painter Leo Whelan. The painting is worth up to €70,000.
The correspondence, written in April 1917, is of immense interest to historians as it contains, in coded terms, Collins' view of political affairs at the time.
They will go under the hammer at Whyte's auction house this evening.
Other items in the sale include drawings by Countess Markievicz, a poster relating to the "Invincibles" and the Phoenix Park assassinations in 1882, a 1922 Civil War Proclamation and a 1922 First Edition of James Joyce's Ulysses.