The mV adjustment knob on my 5020 also looks like that. I think it was original, but I have a nice brushed aluminum Kilo counter knob that I'll probably replace it with.
The misaligned voltage dials are probably a result of slippage. Most of my PD Precision supplies have been a little out of wack, and most of them have been noticeably loose. Loosening the set screws, realigning, and tightening again fixes the problem.
Not sure what, if anything, I'll do about the worn labeling. If I can get some of the old rub-on lettering in a suitable typeface I might try that, and cover it with a coat of protective matte clearcoat.
As for the case, I admit I didn't look too closely at what little was shown. Now that you mention it, I definitely see the signs of chipping/rust. I'm not too worried about dents. I've been pretty successful at banging things out with a hammer and hardwood blocks, though most of my experience is with aluminum, rather than steel. As for the rust, the 5020 I already have was/is somewhat rusted on the case, and the top surface of the transformer core. I'll probably repaint it at some point, but for now, cleaning it off with a melamine sponge and applying some light mineral oil has been enough to stabilize things.
For some sellers "for parts, not working" just means that they don't have the skills / equipment to do proper tests and/or that their business is focused more on volume than maximizing value. For others though, they really mean it. Given that this seller knew enough to show the critical precision components, I think they probably ascertained that it wasn't operational. On the other hand, they may not have gone to the effort to do any troubleshooting. I'll post updates once I have the unit in hand. My hope is that its just a fuse. My fear is that it is the transformer.
Once I receive this supply, with its bubble meter, I feel my collection will cover major variations in the PD Precision Supplies. My 2020s have the proprietary ovenized reference and the old rounded-square GE meter. This 5020 will has the vertical bubble meter (Yokogawa?) and an LM399. My PD 2020b and my existing 5020 have the flat vertical meter and LM399. I think one result is that I have fewer reasons to hold on to any of my 2005a supplies, since the my higher current/voltage supplies cover the same functional and aesthetic territory. Perhaps I'll keep one, just to have an example from the early 70s. In any case, I'll probably finish troubleshooting and functional restoration of those supplies before unloading either or both of them. When I am ready to sell them, I'll let people here know.