VULCAN AUTOSONICS MARK 60 spring powered heat sensitive fire alarm bell
A wax thermostat triggers a bell when the temperature reaches 135 F. The wax can be reset after a heat-activated alarm. There is also a push button to test the alarm. The mainspring should be rewound after every test. This is the MARK 60 model - they also had a Vulcan Autosonic Mk. 30-A Mechanical Heat detector