original 1870's patented ornamental "compression cast" bronze exterior residential doorknob backplate designed and fabricated by the russell & erwin company for metallic bronze company of boston, mass. a total of four matching plates are available with crisp casting and nicely aged patina. the patent date is light incised on the thimbles of each plate. priced individually. metallic compression manufactured "house trimmings", such as knobs, hinges, escutcheons, bell pulls, along with dies for printing wall paper, and for bookbinders, and a variety of articles. the inventions of charles and michael smith, introduced with complete success into practical operation by the metallic compression casting company at their foundry in bomerville, near boston, revolutionized metallurgic art, so far as casting is concerned. by employing the patented process developed by smith and mason, metal was taken from the mould, not with a rough surface, as in all the heretofore known modes of casting, but as smooth and perfectly finished as a coin or medal struck by a die.