Our volunteer squad has a 174 Super Beacon on our in-service Chevrolet/PL Custom ambulance. We need a new skirt for it and also an instruction manual for how to get the glass bubble off.
To remove the dome, remove the three screws that are around side of the skirt. Lift the skirt upwards and the dome will be free. Be very careful, the gasket is probably stuck, and when you pull upwards you do not want that dome to fly up, fall and break.