c. 1920's antique american industrial single wall-mount interior factory complex elevator car "call" push button backplate likely designed and fabricated by or for the otis elevator company, new york city, ny. the unornamented bronze metal backplate contains a centrally located opening for a push button that would "call" the elevator car or cab to that floor. the ruby red glass "jewel" once contained a source of illumination which would switch on when the car was called. the rounded edge backplate has a nicely aged surface patina left untouched since installation in the 1920's. only one available. measures 8 1/2 x 4 x 1/2 inches.