'Just love that exposed PCB with naked connector sockets, terminals with (typically) broken soldering and corrosion of the original 3020 rear panel, don't we? They're certainly classic in the sense that they're still a popular, 40 odd years vintage product but the survivors would surely be a reminder of how not to design a rear panel, however clever and cost-effective it was.
From the rear, this original model looks more like a makeshift patch bay but it does have the convenience of enabling you to read the printed PCB markings so you can make connections from the front side - though not all that helpful when they are under a layer of accumulated dust and grime which is typical of what you find at rear of many domestic audio systems but at it's worst here.