This old piece is cast brass, but it has a grayish color. We have not tried to clean it. This key escutcheon probably was on a door. It is convex and may have come out of the Art Deco era.
The escutcheon measures 2 inches vertically and 1 1/8 inches across. The hole centers are 1 5/8 inches apart. The key hole is 3/4 inch by 3/8 inch.
This is a rarity.