Mystery surrounds a map which experts believe may provide new information about plans to defend England from invasion in World War II.
The map centres on Westerham, near Churchill's home at Chartwell
Auctioneers want help to verify claims made for the document, thought to have been used by Winston Churchill.
The one inch to one mile Ordnance Survey map centres on Westerham, Kent near Churchill's home at Chartwell.
A label on the back says it was "reputedly used in 1940 in connection with the defence of SE England".
Shropshire auctioneer Mullock Madeley, which is selling the map next month, has drawn a blank so far in verifying the map's history.
Experts are appealing for information about the map, which is to be sold at an auction at Ludlow Racecourse on 7 June.
The label claims the map was used by Churchill at "Tall Trees" in preparation for the expected German invasion.
"We have spent a considerable time trying to trace a place called Tall Trees from the archive sources, but at present we have turned up nothing," said historical documents specialist Richard Westwood-Brookes.
"That would normally be the end of the matter, but there are aspects of this which lead me to wonder about it.
"The first is that it is centred on Westerham - which just happens to be the nearest town to Churchill's home at Chartwell.
"One must ask why such a map would be drawn up as Westerham which, as far as I am aware, had no special strategic significance except that Churchill lived nearby."
An arrow on the map indicates a point about one mile south-east of Westerham at a place called Charts Edge.
One theory is that Tall Trees might have been an unofficial identification for a place used to plan the defence of Britain.
"If this is the case, then this humble map might provide historians with an intriguing and new piece of evidence about the activities of Churchill in those very dark days before the RAF pilots won the decisive Battle of Britain," Mr Westwood-Brookes said.