It reminds me of a part originally installed in my home to control the fireplace damper, but being made of brass I seriously doubt it.
My home was made in 1930. If the home it was found in is old, has a fireplace, and has an odd hole in the face of the brick surrounding the fireplace at a height where the damper would be located then stick the thing in and if it fits the damper plate.
A bit unlikely though I will readily admit.