I contacted the person I got Rampage, Checkered Flag, and J.C. Tennis (I also bought Pac-Land and Batman from him). Here is what he said about the items:

 

"Ok, I worked for Tips & Tricks Magazine for 8 years, VG&CE was a part of that magazine at one time, some protos came from there, some from EGM, etc. I don't know precise where all my stuff came from because when I worked at the magazine I went to press events and while everyone got drunk I made contacts and bought up development items...

...But yes, that is the info I have for you about my items. I have over 1,200 protos and al slowly trickling through them and had around 5,000 disk prototypes at one time..."

 

"..." represents edits to his statement I felt appropriate.

Source: Worth of "released" protos