An unusual shape key. All brass. Almost 1 1/2" across the disc. It looks like a key to wind something up. It is larger than all the clock keys that I have, so it would have to be for a commercial size clock if it is for a clock. It's a large opening. I believe it is for an antique mechanical wind-up toy. The edging around the disc is not smooth. It feels like teeth. 2 3/4" long.