Key guns, - Jailers’ keys were filled with gunpowder to create a primitive gun that could be detonated if there was any trouble when opening a cell door.
Viking Age iron key, archeological find from Kättsta, Uppland, Sweden. Upplandsmuseet, Uppsala. http://www.digitaltmuseum.se/things/nyckel/S-UM/UM38601_782?query=vikingatida=24_by==1_filter=Thing=1_context=1=10=7
Key with flintlock. The left side carries clips of belt, as if this “thing” were made to be carried!