There are just two revisions I know of for the Atari PC1, a Revision A and a Revision B. There are no major differences between the two as far as I can tell and an example of the Revision A to compare to the Revision B I have can be found here on bilgisayarlarim.com.
Click on an image below for closer look at the boards.
Atari C100360 – Revision A (1987)
Atari C100360 – Revision B (1987)