Sonic 1 Green Hill Zone #1 @ CES 1991
This footage is from CES and was taken in March 7th, 1991.
This is almost two months before the final build of Sonic 1 and has many never before seen differences in Green Hill Zone. The build also has different DAC samples.
If you are interested in video game prototypes, I welcome you to visit Hidden Palace at http://www.hidden-palace.org/