The silver matrix, which would have been used to impress wax seals on documents, was discovered by metal detectorist Mary O’Grady in 2017. It was found on land owned by Nick Tilt at Ashford Carbonel.
A coroner’s inquest heard the matrix weighed 4.7 grams and was formed of two parts soldered together – the oval face, known as the die, and the handle.
The surface of the die was engraved with the design of a crown positioned above a conjoined thistle and rose.
Shropshire and Herefordshire finds liaison officer Peter Reavill said in his report to the coroner: “There is little or no wear present on the matrix and it has a polished surface.”
The upper side of the die was stamped with a lion shaped mark and some initials likely to be those of the silversmith, but these were indistinct.
Mr Reavill said: “The form of this type of seal matrix is well attributed and dated to the later 17th century.
“Likewise, the use of stamped marks is unusual but becoming more prevalent during the later 17th century.”
He went on to say the design on the face of the matrix die was “symbolic of memorabilia associated with the Act of Union” of 1706, which led to the formation of Great Britain the following year with the joining of England and Scotland, but that "the use of the conjoined thistle and rose is common on metalwork which is broadly dated to the Stuart period".
Mr Reavill concluded that the matrix met the requirements of the Treasure Act 1996 in that it was highly likely that it was more than 300 years old at the time of its discovery and that its precious metal content – in this case silver – was more than 10 per cent, though this had not been tested.
John Ellery, senior coroner for Shropshire, Telford & Wrekin, declared the object treasure.
Speaking after the inquest, Mr Reavill said it was "timely" that the matrix had been discovered at a time when Scotland's continued unity with the rest of Great Britain is uncertain.
He said: "It is quite an interesting find from the point of view of the symbolism of it.
"It celebrated the union of Scotland and England under Queen Anne, and given the fact that Scotland is now desperate to become independent it is timely."
Mr Reavill said the matrix would have been used by people a step up from the general working class, perhaps living in a stately home or estate, to seal private correspondence.
The matrix, which does not bear a family crest or anything personalised, would have been an "everyday item", he said.
Now it has been declared treasure, the matrix will be valued by a committee at the British Museum and the resulting reward split between the finder and the landowner.
Shropshire Museums has expressed and interest in acquiring the matrix to go on display at Ludlow Museum at the Buttercross.