This is an example of a flat sheet metal door key. Looking closely at the first picture, one can see a seam revealing two pieces suggesting an 1880’s date. The key was cut from sheet metal and then folded in half. This process was first patented by Emory Parker on November 2, 1880. I’m not an expert on this topic, but one can learn more by reading “Key Making in the 1800’s” by Richard Chenovick in the July-Sept. 2008 issue of The Antique Lock Collector published by the West Coast Lock Collector’s Association. I have no idea of value, but Chenovick wrote “ These keys are also very collectable as in some cases few were made and consequently they can be difficult to find.”