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.