My first panel was a Selmar Burglar Alarm from 1975.
The bell box was hammered black and only had a synachrome bell inside.
The panel was hammered black and a circuit test button with a green incandescent lamp under the button.
Next to the button there's a key switch with a red lamp under it. Round the side of the control unit was a flick switch and next to it was a xenon lamp.
It was very simple only having two relays , mains and a micro switch.