[Halsol]

Your radio required an external speaker. There were two types used. One was enclosed in a round metal drum like enclosure and it was mounted on the firewall and the other was a smaller speaker mounted with a long cable. It was mounted onto a formed fabric covered metal plate. This mounted in the header above the rear view mirror and the fabric covering it matched the cars headliner. Both speaker enclosures had openings to allow the sound to be emitted. I notice in the power supply section that your receiver has a large metal can type vibrator. This should consist of a two part enclosure held together with a bit of solder at the sides near the bottom. If so, and if need be, this can be opened for inspection by heating and melting the solder while at the same time pulling the top section apart from the bottom base section. At the top right of your photo I can see an externally mounted knob. This should be for tone control. There is available a black wrinkle finish spray paint (it comes in a standard spray can) and if you remove the internal chassis from the enclosure and strip the case to the bare metal, you can refinish the case to OEM appearance.
Hal