A 17th century ring with links to King Charles II, which was found by a metal detectorist, is expected to fetch around £10,000 at auction.
Michelle Vall from Blackpool, Lancashire, found the treasure at Duck Bay on Loch Lomond while exploring the area with her husband.
She declared the ring to the Scottish Treasure Trove Unit at the National Museum of Scotland but was told in June this year the museum did not want to buy it.
After it was returned she contacted auction house Dix Noonan Webb (DNW), which discovered the crest belonged to the Colman family of Brent Eleigh, Suffolk.
The ring, found last November, is thought to have belonged to Edward Colman, who became a convert to Catholicism and was later found guilty of treason and hung, drawn and quartered.
Mrs Vall said: “Uncovering the ring was an unforeseen event as myself and my husband were detecting on a field with no particular history of finds in the area.
“We were enjoying the peace and relaxation of our wonderful hobby, finding the usual ring pulls, tractor pieces and miscellaneous metal objects.
“So when I unearthed the ring, which was close to the surface, I knew straight away that it was something special.
“It shone with a distinct bright yellow colour as I carefully lifted it out of the dark muddy hole, where it had waited for at least 350 years.
“My calm mind changed to one of excitement as I shouted Tony over, he was surprised to see the ring lying in the palm of my hand.”
The inside of the ring is engraved with I for Jesus, which could indicate the owner was a member of the Jesuits.
Edward Colman established himself at court in 1661, acting as a bodyguard to the king, and by 1673 had been appointed secretary to fellow Catholic, Mary of Modena, wife of James, Duke of York, the younger brother and heir presumptive to the Protestant King Charles II, who reigned from 1660-85.
During the end of the 1670s, James and Mary had been living in Edinburgh and in 1680 the king made James Commissioner for Scotland.
In September 1678, Titus Oates made fanciful claims of a “Popish Plot”, accusing nearly 550 Jesuits of involvement in plots to assassinate the king, with Edward Colman among the accused.
He was found guilty of treason and in November 1678 was hung, drawn and quartered.
Nigel Mills, a specialist consultant at DNW, said: “The ring is in amazing condition, it was lost when it was virtually new and has not suffered in the ground.
“We believe the ring belonged to Edward Colman who was the secretary of Mary of Modena, wife of the future King James II.
“They lived in Edinburgh so it’s likely that is the reason why the ring was found at Loch Lomond.”
He added: “It’s the excitement of the find as no-one would have touched it since he lost it.
“It’s like shaking hands with the guy, it really brings it to life.”
Now considered to be a Catholic martyr, Edward Colman was beatified by Pope Pius XI in 1929.
The ring, thought to date from 1640-80. will go under the hammer in DNW’s Jewellery, Watches and Objects of Vertu sale in London on September 10.
It is not the first time Mrs Vall has found a valuable object.
A few years ago she found a rare gold half angel coin struck during the reign of the Richard III, which sold at auction for £40,800 in December 2017.