Members of Hemingby History Group were overjoyed after securing a letter written by legendary Horncastle hangman William Marwood.
They saw off rival bidders at an auction in Louth earlier this month.
The fact they were successful seemed fitting as in the letter, Marwood offered his services to hang William Drant, a Hemingby man.
Drant had been found guilty of murdering Hemingby’s police constable Thomas Gell in 1876.
However, the group’s delight turned to dismay when an eagle-eyed member spotted the letter was not all it seemed to be and was alledgedly a ‘later copy’ of the original.
Now, the group has secured a full refund - and has promised to learn from the experience.
Group chairman Alison Fairchild said: “When we saw the article in the Horncastle News about the letter being auctioned, we thought it would be ideal to add to our collection.
“It was a very busy auction and the auctioneer said it was the star item so we were delighted to secure it.
“However, a member of our group compared the letter with other examples of Marwood’s writing online and we realised ours was a later copy.
“We contacted the auctioneer and happily everything has been resolved.
“The auctioneers and the sellers were very helpful and we have a full refund. It was an innocent mistake.”
She added: “We are disappointed it wasn’t an original. If anything like this comes up again, we shall know to check online to see if there are any examples of previous letters to compare with.”
James Laverack, a spokesman for the auctioneers, John Taylors, confirmed an agreement had been reached but declined to comment further.
Marwood was appointed by the government as a hangman in 1872.
In nine years, he hung 176 people.
Originally, a cobbler, he lived in Church Lane, Horncastle.
He died in 1883 from pneumonia and jaundice and was buried at Trinity Church.
He never got to hang Drant, who was handed a reprieve because he was found to be suffering from epilepsy at the time of the murder.
His case signalled major changes in the British legal system.
Constable Gell was buried in Hemingby churchyard.