An apparent attempt to remove a replica Stone of Destiny from Scone Palace in Perthshire has been unsuccessful.
Tayside Police said the stone was taken and replaced with another sometime between Wednesday and Thursday.
The replica stone was later found dumped in the grounds of the palace although its brass plaque was missing.
The real stone, on which Scottish monarchs were crowned, was removed by Edward I in 1296 and fitted into a wooden chair at Westminster Abbey.
It was stolen from there by a group of Scottish students in 1950, later turning up on the altar of Arbroath Abbey more than four months later.
In 1996 it was returned to Scotland as a symbolic gesture and is now kept at Edinburgh Castle.
The replica stone at Scone Palace is generally sited outside the chapel on Moot Hill.
Its plaque reads: "A replica of the stone upon which the Kings of Scots were crowned on Moot Hill until 1296 when Edward I took the stone to Westminster Abbey.''
A spokeswoman for Tayside Police said: "It is a very unusual incident and officers are currently making enquiries into the possible motivation for someone swapping the stones.
"Both of the stones are of considerable weight and would require at least three to four people to carry them.
"Transport would also have been required."