The power of X by Arthur Sellings hardcover 1968 Vintage Science Fiction
The year is 2018. The place is London, where a renamed Buckingham Palace is now the home of the President of a European Federation of states.
An outstanding feature of life in London in 2018 is Plying--a recently discovered method for producing duplicates that are absolutely indistinguishable from the originals. For a variety of reasons, mainly the staggering expense, Plying is limited to valuable works of art, intricate industrial mechanisms, etc. And the process is a highly guarded government monopoly.
Then a young art dealer named Max Afford discovers that he can tell an original by touching it! Bowled over by his unique gift, but unable to profit by it, Max first decides to forget the whole thing. But a shocking incident forces him into action--action that lands him in the middle of a plot to break into Europa Palace in the hope of saving this Plied society...
