I contacted the collector I got Blue Lightning, Basketbrawl, Road Riot, Fat Bobby, and Shadow of the Beast from, here is what he said:

 

"...I got them from 3 different sources over the years, one set from Curt Vendel (many years ago...) who got them from John Skruch .

Another set directly from Juli Wade. Skruch and Wade were both producers at Atari, and I'm sure you'll recognize their names from various games' credit screens.

A third set came from an UK seller. I forgot his name but I believe he was coordinating UK developers as all the protos I got from him were games that were programmed by UK teams (SotB, Road Riot, Fat Bobby)...

Blue Lightning Demo came from Juli Wade, Basketbrawl from the John Skruch set."

 

"..." indicates edits to his statement that I felt were appropriate.

 

Here are some more protos that look similiar that I picked up from a fellow who said he got them from a liquidation asset auction. He couldn't give me any more info on them.

I tried to get some clearer pictures of these, than the last ones

Source: Worth of "released" protos