This is a very unusual cast-iron key hole escutcheon for a passage door. It is definitely from the Eastlake era (1870-1890). This piece would accent or accompany the cast iron back plates used behind an Eastlake door knob or a black porcelain knob that was popular during that time, as well. The key escutcheon was used on the backside of the door under the door knob and rosette.
The piece measures 2 1/4 inches vertically and 3/4 inch horizontally. The key hole opening is 11/16 inch long. Steel screws will be included for mounting.