Heh, I'm going to have to figure out a way to upscale it to the size of a page but that will look great on the wall!
Anyways I had to get it home to do more work on it, plus photos, so here are some of the cleanest photos you'll probably find on the internet.
This particular unit was manufactured in February 1980, four months before Pioneer would release the VP-1000 and likely not long before PR-7820's stopped selling under the DiscoVision brand and instead under the Pioneer PR7820 Model I/II/III name. I do not unfortunately have the remote.
I cannot really proceed much further until the rubber hub bumper is replaced. A suggested replacement was part of a bicycle inner tube as opposed to an O-ring. I need to dig through the service manual (I found the FULL thing, it's 135mb!) on how to remove the spindle for cleaning but I cannot proceed to the laser issues until then.
Like I mentioned with my initial check the laser is good. The mirrors were oh-so carefully cleaned but with a disc loaded the focus assembly drops down and then snaps back up to try again. It does it as well with a disc not loaded (the machine lacks a disc presence sensor so you can operate the unit without a disc installed) but is a lot gentler with the focus attempt, so it does know SOMETHING is spinning but I can't tell if it's because of a pickup issue or the molten bumper causing the disc to wobble too much to permit tracking.
The laser is also delightfully dangerous.
The only other thing I still need to research is that there is a battery in the unit! It's behind a panel underneath at the lowest point of the machine where a leak is acceptable and it's easy to clip the leads and remove. I have no idea whit it might be for aside from keeping the 1K dump memory alive for short periods of time.