Treasure trove is a technical term in English
law. Under
common law, any
treasure (roughly anything found that is old and contains
precious metal) had to be the subject of an
inquest, presided over by a
coroner, to determine whether it is lost, or deliberately
hidden.
If the items were lost (including casually or carelessly abandoned), they were up for grabs, and it was a case of finders keepers. But if the coroner determined that a person or persons unknown deliberately left them there with the intention of one day getting them back -- and in the days before banks this was normal practice -- then (assuming the original owner could no longer be traced) the treasure was treasure trove and belonged to the Crown. The Crown would reward the finder.
Under the Treasure Act 1996 the legal standing of treasure trove was abolished, and treasure was defined as any object over 300 years old and containing at least 10% gold or silver. Single coins are exempt; two to nine coins fall under the precious metals rule; ten or more coins are treasure regardless of content. All treasure belongs to the Crown regardless of the original owner's intentions. The Crown rewards the finder with something like the full value, in order that important national patrimony and antiquities not be lost.
Failure to report treasure is punishable by three months' imprisonment or a 5000 pound fine. The new Act applies to treasure found in England, Wales, and Northern Ireland on or after 24 September 1997. A coroner's inquest is still required: in England the coroner notifies the British Museum.
The adjective trove is Law French for 'found'.