Rosedale Show may not have the livestock entries of many other shows, but it more than makes up for it with its ambience and the splendid setting of the village of Rosedale Abbey, often described as "a little piece of heaven".

The show goes back to 1871, but visitors who come here at other times of the year are often looking for something much older – they want to find the abbey, but they never do.

It never existed. There was a medieval nuns' priory – established in 1154 and dissolved in 1536 – and all that remains of that is a stair turret. Over the years, pieces of the old priory have been found in the village church and local buildings. The priory's 14th-century tracery window was built into the outer wall of the sacristy of the present church, overlooking the school playground, and old priory window jambs have been used as gate posts at a cottage opposite the Milburn Arms Hotel.

It's not that often a piece of the remains is discovered. So when a beautiful old piece of carved stone was dug up, amateur historians in Rosedale were delighted.

Residents feel sure that the 50x30cm mystery stone is from the old priory, and, according to one expert, David Haddon-Reece, it is certainly in the style of 12th- or 13th-century architecture. But it is also possible it is from the 19th century, a period when stonemasons copied medieval buildings.

Duncan Herd, a local author who has researched the story, believes that the shape of the stone is a strong indication that it once belonged to the priory.

And Mr Haddon-Reece, formerly head of English Heritage's geophysics and dating section of ancient monuments laboratory in London, and a resident of both Rosedale and Thirsk, believes the stone is interesting enough for further research, and is consulting with fellow experts to establish its identity.

The stone was found by Andrew Claughton, a labourer for Sid Brackley Builders, of Kirkbymoorside. He was rebuilding an old paraffin store for Abbey Stores and Tea Room when he came across it.

"It was well down," he said. "It was underneath the foundations – not part of the foundations. Fortunately, I didn't break it."

The builders and Anne Wright, owner of Abbey Stores, have displayed what they call the "precious find" in a specially made recess on the front of the new building – Abbey Bike Hire – so visitors and local residents can see it. The newly formed Rosedale History Society has sent photographs to a church specialist who may be able to date it.

To assist puzzled visitors searching for an "abbey" – the North-East Yorkshire Geology Trust, in conjunction with the Rosedale and Hartoft Community Group, are developing trail guides with interpretation boards marking key historical locations. The Geology Trust has been awarded a £60,000 grant from the Heritage Lottery Fund for their design of a "Vale and Dale" project exploring Rosedale's earth heritage.

The money will also be used for training members of the community, public events, a heritage booklet, and a display at Molly's farm shop in the village.

If the project is successful, it will be a fitting tribute to a group of women Duncan Herd believes history has forgotten. "The remarkable thing about these priories is that the women who ran them get no credit whatsoever. For 350 years, these ladies in Rosedale ran a very successful priory," he said.

Writers, says Mr Herd, often refer to a nun who became pregnant or a nun who wore a brightly coloured scarf. But they ignore the fact that Rosedale Priory had more than 2,000 sheep, as well as cows, calves, oxen and horses; exported 2,000 fleeces to Italy every year; employed a labour force of about 70 and owned 40 farms and six mills. The nuns were "women of steel", he said.

The nuns, however, are not forgotten by the 20 children at Rosedale Abbey Community Primary School who know that some of the women are buried under their playground in the old cloister. And it is the hope of Duncan Herd and another Rosedale resident, Colin Westwood, that one day there will be a stone model of the old priory at an open-air site in the village for all residents and visitors to see.

Mr Westwood, secretary of the community group, is looking into the potential of building two models of Rosedale – one of the old priory and another of the 1865 Rosedale mining village. Mr Haddon-Reece owns what he believes to be two pieces of the old priory – a piece of window or door jamb with dog-tooth decoration, and a well-carved, semi-cylindrical stone shell, which he believes was part of a culvert.

He is certain it is ecclesiastical, and because it has been found in the country, he believes it is either from the priory or from the top of a 19th-century gravestone or building.

"It does not make great sense on its own," he said. "It was probably part of something such as a tomb, but there is not enough to make a clear diagnosis. It is most likely a gable finial. It is perfect in style for the early 13th century or late 12th century, but it could also
be from the 19th century Gothic revival. The fact that
it is crisp and clean makes it a puzzle."

A resistivity survey of the Turret Field next to the present-day church was conducted in 1993 by the electronics department of the University of York, but it was inconclusive in revealing the priory's foundations.

What might be more useful is a three-metre ground-penetrating radar survey. That could successfully examine the Turret Field. However, permission would be needed from the church authorities to analyse the churchyard, and it could be impossible to examine the south side of the church because it is covered in asphalt.

The priory buildings were still a landmark until the mid 19th century. But as the village became overwhelmed by iron mining and smelting operations, the incomers used the priory stone for new buildings, and the home of the nuns melted away.

Historians can't bring back the old priory, but they can revive its spirit.

Rosedale and District Annual Show, in Milburn Arms Field at Rosedale Abbey, open 9.30am. Admission to show and sports £4, seniors £3, children £2, under-fives free.