Computer Reset has been a treasure trove of PCjr stuff, including some prototype PCjrs and historically interesting ones. I had the good fortune to stumble upon some rarities myself.
Here is an overview of the prototype PCjr system unit I found as well as some very odd keyboards. I'll compare each item to its normal, retail version.
Exhibited at the DFW Retrocomputing meetup on 25 January 2020.
(I apologize for the poor quality of the photos. I did them in a rush with bad light and a lousy camera that couldn't hold a set white balance.)