This collection of parts is the major components of an installation. It is sitting upside down on a tool box. The side facing the viewer faces the cockpit. It bolts directly to the firewall so original cars have either four small AerotightŪ stop nuts and washers showing on the engine bay back wall or four small holes were a heater use to be mounted if the original fire wall is intact. The mounting flange is part of the outer housing and not anything separate.
If the car had a factory installed radio, the radio was at risk if coolant leaked inside the case for any reason. Leaking coolant would make its way down to the rounded protrusion on the motor case and drip on the top middle of the radio.