A blow-off plate. usually attached to the lower plenum of an intake manifold that has a 671 attached to it.
Yup, one of those old alarm sensors that set off the horn if you bumped the vehicle.That is an old school motion sensor alarm.
It connects to the horn circuit.
That little screw on top adjusts the sensitivity.
Basically just an arm inside that is suspended by a spring, and when the car moves the contacts touch making the horn honk.
They kinda sucked actually.
Dadeland Dodge!!! I knew that place. Miami, FL.