What does it mean?

      A rather fine and tasteful example of an Edwardian letterform although in my opinion it does have a certain funereal quality to it, perhaps because of the black inlay of the letters in white marble.
      This plaque is high in the apex of the house it adorns and in turn it is quite a discreet piece of work. The amazing thing is the way that it has stood up to the ravages of time and climate, all-in-all a masterful piece of work, but just what does U.D.P. mean? Ulster Democratic Party? A builder or an architect's initials? Perhaps more research work is required.
      Meanwhile, well done that stonemason.