The material, which was acquired over half a century by Ballina businessman Jackie Clarke, spans nearly 400 years of Irish history and contains items historians didn't even know existed. The collection contains many rare books and manuscripts and includes one of 20 surviving copies of the original 1916 Proclamation.

Before he died in 2000, Clarke requested that his collection be made available to the people of Ireland.

"He had a great passion for history, " Anne Clarke, his widow, told the Sunday Tribune last week. "Jackie was an idealist who wasn't interested in money."

The oldest manuscript in the collection dates from 1617, while two handwritten letters from Wolfe Tone are dated from 1798. There are many unique items relating to the 1916 Rising. They include a letter requesting a priest give Padraig Pearse the last rites before his execution in May 1916, correspondence used by the British military as evidence in Eamon Ceannt's court martial, and books from Joseph Mary Plunkett's own library including what appears to be a previously unpublished poem in Plunkett's own handwriting.

The collection also includes an autograph book with the signatures of all the members of the first Dail. On 7 January 1922 . . . the day the Dail ratified the Anglo-Irish Treaty . . .

Michael Collins wrote in the autograph book: "Let the Irish nation judge us now and for future years."

The boxes in the collection are filled with thousands of handbills and leaflets covering all eras of republican history, including a 1910 notice from New York featuring a very rare picture of a young James Connolly. In 1993, seven years before his death, Clarke acquired a copy of the 1916 Proclamation. "It was his pride and joy. He called it the 'holy grail', " his widow recalled.

The Clarke family has decided to donate the collection to the state and Mayo County Council is providing a multimillion euro budget to transform the old Moy Hotel building in Ballina into a modern library and research centre. The Jackie Clarke Library will be officially opened next October. Work on cataloguing the collection is currently being undertaken by the historian Sinead McCoole, who has been appointed Curator/ Keeper of the collection. She has spent the last nine months sorting through the material.

"I had the amazing opportunity of opening three locked rooms in Jackie Clarke's home and sorting through boxes stacked to the ceiling, and unwrapping brown paper parcels, " said McCoole.

Clarke, who was born in 1928, was actively involved in republican politics and was a member of Ballina Urban District Council for almost two decades. He also ran a successful fish processing business in the Co Mayo town.

He acquired many items from dealers at a time when Irish historical material attracted far less buyer interest than in recent years.

An auction of almost 500 lots in Dublin this week, which includes the Kathleen Clarke papers and an original copy of the 1916 Proclamation, is expected to realise over 2m.