Brass buttons reportedly found in Irish revolutionary leader Michael Collins's pocket on the day he was killed are to be sold at auction among a collection of Irish-themed valuables.

According to the Irish Independent, the buttons, which are expected to fetch between $2,000 and $2,600, come with a signed note to General Eoin O'Duffy from Michael Collins's sister, Margaret Collins Powell.

The note reads: 'Please send me a receipt for the enclosed, found in Michael's tunic pocket, August 22, 1922.'

This was the day Collins was assassinated in Beal na Blath, County Cork.

The buttons come as part of a larger collection of items which once belonged to the former IRA Chief of Staff O'Duffy, including the last truce that O'Duffy negotiated with the Anti-Treaty side in 1922 and other personal items.

But all of O'Duffy's belongings in the collection nearly ended up on the scrap heap as the current owner of his estate lives in Norway and didn't realize their significance or value at first.

The auction, entitled 'A Gathering of Things Irish Sale' will be held on July 23 at the Clyde Court Hotel in Ballsbridge, Dublin at 10.30AM.