This is an antique cast brass doorbell, the doorbell unscrews from the mounting plate, there are two screw holes on the plate for easy installation. Typically placed near a door to a building's entrance. Although the first doorbells were mechanical, activated by pulling a cord, modern doorbells are generally electric. Only one available, the electrical component is untested the item is sold as is however the wiring is in unknown condition and will need to be rewired as no leads are available. Two tiny holes were drilled into the back plate as shown in the photo.