I really believe the art work is painted on because it has flaked off in some spots. Its just like the Berzerk bezel, I believe it was done at the same time. I have heard that even water can destroy this artwork.
If I know how to get the Mr. Do stuff off, I'll put a protective coat on the Astro Invaders artwork before Mr. Do removal. But like I said this stuff is really hard. Any ideas of what to use?