When Shropshire metal detectorist Chris Langston heard the tell-tale beep of his device in a field outside Oswestry last year, he thought it was nothing unusual.

It had picked up a small, heart-shaped object that he thought could have come off horse tack and fallen into the ground.

However, on closer inspection Langston noticed there was an engraving of a heart with two arrows piercing it and a single drop of blood underneath, and realised it could actually be something special.

A year later, it has been declared as treasure and will go on display at a museum, where he said an official told him it looks like "a memento mori locket to commemorate the death... of Charles I in 1649." .

"It's just an amazing find," Langston told the BBC.

King Charles I was tried and executed following his defeat in the English Civil War, in 1649.

In the aftermath of the war, the monarchy was abolished, and England was governed as a republic, and for those who remained loyal to the king, their expressions of this became much more private.

The British Museum said that Royalists, also known as Cavaliers, would have small objects such as medals, rings and heart-shaped lockets, which carried Charles' portrait alongside inscriptions including "I live and die in loyaltie" and "Prepared bee to follow me".

It said they were worn or kept close to the body as "intimate expressions of loyalty in a period when Royalist belief sat uneasily within the new political order."

"Essentially, it's the front of a locket which somebody like a Royalist would've kept about their person, hidden away, because you'd get into a lot of trouble having one of these now the commonwealth had taken over," said Langston.

"This thing that I found is the front of a locket - the missing part is the piece that would've been attached to the chain on a loop and inside that missing part… would be a little pressed portrait of King Charles I," he said.

"Just to keep the faith."

The item was declared treasure recently at the conclusion of an inquest by a coroner.

"In my case with all of my treasure finds I always waive the fee," said Langston.

"I get so much out of the hobby without taking any money from it.

"It's back in my possession.. they've [British Museum] already got one of similar example so they don't need it."

He said he would be sending the locket piece straight to Oswestry Town Museum to go on display alongside many other finds he had made.

Follow BBC Shropshire on BBC Sounds, Facebook, X and Instagram.