This is a large cast-iron key escutcheon. It may have been used on a large, heavy door, or it could have come off of a large chest or trunk. It is unique, to say the least.
The shield-shaped escutcheon measures 2 inches across the top. It is 2 1/2 inches vertically. The hole centers are 1 3/4 inches apart. The key hole looks like it could accommodate a fat trunk key. It measures 7/8 inch vertically and 3/8 inch horizontally on top and a skinny 1/8 inch on the bottom.
Jewelry makers, who says this antique has to be used on a door or trunk? Black screws will be provided upon request.