It was the finest moment in the history of Bradford City Football Club and now a unique piece of memorabilia from the most famous game is up for grabs.

The medal given to captain Jimmy Speirs after he scored the only goal in the club's 1911 FA Cup win goes up for auction next month.

His Canadian granddaughter Constance Hamilton Wills will be accepting offers for the medal on internet auction site e-bay between November 6 and November 16.

A medal belonging to Speirs' team-mate Frank Thompson sold earlier this year at Sotherby's for £22,800, four times its estimated value, and it is thought interest in this item will also be high.

But Mrs Hamilton Wills, an antiques dealer, had no idea her grandfather was so famous and said she was overwhelmed with the response when she first listed the item on the site in June this year.

"At the time I knew absolutely nothing about football," she said. "I had absolutely no idea of the importance of the FA Cup and this particular medal, nor did I realise that my grandfather was a football hero!"

It is being offered for sale along with Speirs' Glasgow Charity Cup Winners' medal, won with Rangers in 1906, and his First World War service medals.

Medals won by his son, also called Jimmy, while serving in the Canadian Army during the Second World War will also be auctioned.

The auction would have gone ahead unnoticed if Mrs Hamilton Wills had not been informed of the importance of the medal by a Bradford City fan who had read about the Frank Thompson sale in the Telegraph & Argus.

She withdrew the items from sale, and started looking into her grandfather's history.

Bradford City's managing director Shaun Harvey said he would love to see the medal return to its roots, but added that the club would not be making an offer.

He said: "This is a very important item in the club's history. A lot of interest will have been generated by the Frank Thompson medal sale and we will make it known in our programme that this is now available.

"The chances are that it will be a Bradford City fan that buys it."

And City fan Dave Pendleton, who is also the joint organiser of a current exhibition marking Bradford City's centenary year, said that he would love to put in an offer but would be unlikely to be able to match the price it would go for.

"I would be delighted if a Bradfordian bought it though and it remained in the city," he said. "It would be wonderful if it could go on show in Bradford."

The 1911 victory marked the peak of Speirs' three-and-a-half year career with the club, which rose to its highest ever position in the league - fifth in the first division - during that season.

The FA Cup final was held at Crystal Palace on 22 April against Newcastle United, one of the giants of the game in that era.

But the game finished in a goalless draw and a replay was held the following Wednesday at Old Trafford. The only goal came courtesy of the Scottish striker after 15 minutes.

The following year Speirs was sold to Leeds City FC and played his last match in the 1914-5 season. He left and joined the army, and died while serving with Cameron Highlanders in the First World War, aged just 31.

Potential bidders for the medal can register their interest and request further information from Mrs Hamilton Wills via email at sea@georgian.net.