Another copy of the original 1916 Proclamation of Independence is to go on sale in London next Thursday, after a similar copy made €390,000 at an auction in Dublin on Wednesday night.
Half a dozen under-bidders from Wednesday's auction are expected to place bids at next week's sale in Sotheby's for the copy, one of only 20 believed to exist.
The Sotheby's copy is in better condition than the one auctioned by the James Adam saleroom on Wednesday and it was authenticated and signed by the printer of the proclamation, Mr Christopher Brady, in 1969, shortly before he died. It is being sold by an Irish family.
The identity of the successful bidder on Wednesday, who paid well over twice the reserve price of €150,000, is not known.
Five hundred copies of the proclamation were printed for the Rising, and just 20 are believed to have survived intact, three of which belong to State institutions, including the National Library and the National Museum.
Wednesday's copy was bought over the telephone by an agent on behalf of an Irish client. The owners of the copy, which had been kept in an attic for nearly 60 years, were at the sale.
The Adam's sale has increased interest in the Sotheby auction next Thursday. Rare books expert Mr Peter Selley said the value of the proclamation had been rocketing in recent years.
In 1997 Sotheby's sold one for stg£30,000. Another record was set in December 2003 when one was sold for stg£55,000, surpassed just six months later when stg£110,000 was paid for one, again at Sotheby's.
A spokesman for the dancer Michael Flatley, who has previously said he wanted an original proclamation for his library at Castlehyde, said he was not Wednesday's buyer.