The legal position
Under the regalia minora common law rights of the Crown in Scotland, it is the prerogative of the Crown to receive all lost and abandoned property which is not otherwise owned.
There is a narrow definition of treasure trove per se, involving precious items which have lain concealed, but in practice this is overridden by and subsumed within the wider legal concept of bona vacantia (or ownerless goods).
The crucial maxim within Scots common law is qoud nullius est fit domini regis (that which belongs to nobody becomes our Lord the King's [or Queen's]). Thus all objects whose original owner or rightful heir cannot be identified or traced are the porperty of the Crown. It does not matter whether objects were lost or intentionally hidden, or what material the objects are made of.
The Crown Office in Scotland has the duty, overseen by the Scottish Executive, to claim bona vacantia on behalf of the nation. Archaeological finds and historic objects are just one part of the work which the Crown Office does under bona vacantia, which includes such matters as intestate estates.
Operation of the Treasure Trove system
The system whereby archaeological objects are dealt wiht under bona vacantia is know for convenience in Scotland as treasure trove, though it is important to distinguish it from the Treasure Act 1996 in England and Wales (see under website links), which does not apply in Scotland.
In order to exercise its rights over archaeological finds under bona vacantia, the Crown Office relies on the recommendations of an expert group known as the Scottish Archaeological Finds Allocation Panel (SAFAP). Members of the Panel, who serve voluntarily, are appointed by the Scottish Ministers. The Panel has an independent chairperson, currently Professor Ian Ralston, and four members drawn from the museum and wider heritage community. The members do not represent any sectional interest, being appointed on the basis of the expertise and experience the can bring to bear.