Padraig O’Shea, who runs a collectors’ shop in Cork, took the snap decision after he was approached with an offer to buy one sheet of 60c stamps that was bought at face value six days earlier.

The special edition stamps were released by An Post only to be withdrawn almost immediately.

The 60c Citizen’s Army issue was supposed to go on sale last Thursday, but the plan was halted when historians raised doubts about the image chosen.

An Post had believed the picture on the commemorative issue was of Captain Jack White, a former British army officer who volunteered for the Irish Citizen’s Army in 1913.

But when the image was circulated on Jan 22, historians said the man in the picture was not Capt White.

Mr O’Shea, who runs the Collectors Centre on Washington St, understands in a small number of post offices, the stamp was on sale for less than 10 minutes before they were withdrawn.

One of those who bought stamps approached the shop yesterday with a sheet he wanted to sell. “He is a client of mine, he said he bought them within 10 minutes after the stamps went on sale.”

Mr O’Shea said he had been in the business for 30 years. He tried to verify the number of stamps circulated but could not get confirmation.

It meant that while there was no way of knowing the real value the sheet, he decided to trust himself.

“You have to back your knowledge in these situations; you are buying something in the hope that it has collectors’ value.”

He said as far as he knew, the circumstances were unique as no other Irish stamp was withdrawn having been available in such short supply.

He said in 1989, An Post had planned to release a stamp for the 200th anniversary of the French Revolution but it was blocked at a late stage by Cabinet, because of poor relations at the time with the French government. It never went on sale.

He said in Germany, there was a similar decision where a very small number were circulated in advance. These stamps have gone on to sell for up to €20,000.

An Post said it has withdrawn the stamps while it clarifies the issues raised, and does not know how many were sold. “Post offices were advised not to offer the stamp for sale on the morning of issue but it is possible that some may have been sold,” it said.

“Where or how these stamps may subsequently be traded or sold is not a matter for An Post.”