Catering manager Caroline Parkinson, 61, of Telford has a passion for history and has been going out metal detecting for about four years.
"My partner surprised me with a small metal detector about four years ago and I go out most weekends and during the week when I can," said Ms Parkinson. "I had always wanted to do it. I have found plenty of things but this is my first treasure.
"I would like to go out every day but work gets in between me and my detecting."
Ms Parkinson's long-term partner, Alan Adderley, 56, doesn't share her passion however.
"He's a digger for overhead power lines, so going out in a field digging is the last thing he wants to do," she said.
But her hobby really paid off on Sunday, January 22 this year when she joined a group of about 60 other metal detectorists and headed into a field owned by the Robinsons at an undisclosed location near Hodnet.
After her detecting machine gave a characteristic beep, she found the brooch about four inches down. It was an organised event with the full permission of the farmer involved.
"I thought it was a piece of costume jewellery until someone else told me he thought it was treasure. I'm very excited to have it declared treasure but we don't know how much it will be valued at," she said.
"I know the museum wants it and I would love for it to go on display so I can go to see it."
Richard and Isobelle Robinson own the field and will share the proceeds of the sale.
Mrs Robinson said they are happy to get appointments to visit and detect on the land and see people out in the countryside enjoying it. "It is nice to let people enjoy their hobby," she said.
The secret field in question is cultivated but had never been subject to metal detecting before, and Mrs Robinson said more items were found that are going through the process of being declared treasure. Metal detectorists have to have insurance, she added.
Shropshire's senior coroner John Ellery declared the medieval silver gilt annular brooch treasure at an inquest at Shirehall, in Shrewsbury, on Thursday. He heard evidence from Dr Ian L Bass, the Finds Liaison Officer for Herefordshire and Shropshire.
His report said that annular brooches with animal designs can be dated to the thirteenth century (1200–1300).
Because it is more than 300 years old and has a content of more than 10 per cent of a precious metal it qualifies as treasure, Mr Ellery said. It has a double headed animal design with a saltire cross, is 24.84mm across and weighs 4.51 grammes.
Dr Bass said this treasure case represents but a small fraction of the work of the British Museum’s Portable Antiquities Scheme whose Finds Liaison Officers record and identify archaeological finds discovered by the public.
"In this case the find was discovered by responsible metal detecting," he said.
"This annular brooch bears zoomorphic decoration in the form of two confronted double-headed animals. It has been made from silver, with gilding on the surface.
"The saltire crosses placed between the double-headed animals contain traces of the original niello - silver oxide which would have appeared black - now dark grey in colour.
Shropshire Museums have expressed an interest in acquiring the find under the Treasure Act 1996. Now the find has been declared treasure it will be valued by the Department for Digital, Culture, Media, and Sport’s Treasure Valuation Committee.
Councillor Rob Gittins, Shropshire Council cabinet member for culture and digital, said: "We are delighted the medieval brooch has been found in such remarkable condition and that the finder acted responsibly in reporting its discovery.
"It is always incredible to discover what has been hidden under the county's land and we look forward to being able to acquire this piece so that it can be put on display in Shrewsbury Museum and enjoyed by everyone."