Got to sit in one once at a car show, back in ~90.
Sorry for the crappy phone pics, but here's my Clarion CDC6500R.
This is a UK version I believe.
A special wire harness, it's hardwired directly from the HU plug to the "factory" plug.
The serial number stamped into the cage.
Owners manual in 6 languages!!!!!
I will soon have some pics of a newly acquired Clarion 6770. It had a bad board in the face, so I had to buy a replacement face off of ebay which showed up yesterday and it works 100%. This was my first ever HU back in '92.
Thanks Bret, I have another PPI one like the last one I scanned, The last brochure had the PPI AM amplifiers the other brochure has the M amp's in it. But it was getting close to 4:30 in the morning so I figured I would quit for the night (day), lol