It has a face value of ten shillings but a price tag of Aus$3.5m (£2.3m) at Coinworks, the specialist dealers and auctioneers of Melbourne.
This banknote, the first ever printed for the official Federation paper currency of Australia, is being offered for private sale.
It was discovered in 1999 among the effects of the Honourable Anne Judith Denman, who had died 12 years earlier. How she came by note M000001 is a matter of well-documented record.
On November 5, 1910 the Commonwealth Gazette announced a competition for the design of new ten shilling, £1 and £5 notes, the first official Federation paper currency. The prize was £50 for each denomination.
However, no entries were considered suitable and so note-printers Bradbury Wilkinson & Co were given the task. Three years later the Commonwealth Government launched its distinctive new currency.
The Number One note was hand numbered at an official ceremony, also pictured here, held on May 1, 1913, at the Government Printing House in Melbourne (now Queen's Warehouse).
The dignitaries present included Prime Minister Andrew Fisher and Governor General Lord Denman, who was accompanied by his children Judith and Thomas.
The honour of hand-numbering the first note, M000001, was passed to the Governor General's five-year-old daughter Judith Denman, and the note was subsequently presented to her by the Prime Minister.
Lord Denman numbered and received note number M000002, and seven-year-old Thomas numbered and received note M000003.
Andrew Fisher purchased notes M000004 and M000005, for which he paid the face value of £1 with a sovereign from his pocket.
It was intended that the hand-numbered notes M000006 to M000500 would be allocated to members of parliament and other dignitaries by way of a ballot.
As only 22 hand-numbered examples have appeared over the last 50 years, it is clear that not all were taken up, with many of the notes slipping into circulation and ultimately being destroyed.
Lord Denman resigned his position as Governor General in 1914 and the family returned to England.
As has now been discovered, his daughter kept the note all her life and it turned up in a letter file housed in a contemporary Government House envelope marked in pencil "Judith's 10/- Note May 1st 1913".
The Number One Note, which last sold for Aus$2m in 2008, is offered with the accompanying historical envelope.