It's stranger than I originally thought!
Ok, here goes:
Part showing applied Maxwell material - "shiny black plastic" - note the "real material" circled in yellow; 6061 alloy

Now, with the goofy ASCII code all over it:

Now, the best one; when I just saved the part as a jpeg (not screen capture, the ASCII stuff doesn't show up!

It "seems" like - maybe; apply a "real" material, 6061 alloy (this by itself changes the way the part looks), then apply a Maxwell texture. It will look correct on the part. Open an assembly with the part in it. The ASCII stuff shows up. Open the part and confirm the ASCII stuff is there. Remove the Maxwell material - no change. Remove the "real" material; the part goes to a default color. Reapply Maxwell material; no problem.
As it *may* be, I may have applied a new Maxwell material over the "real" and previous Maxwell material. I don't remember exactly but that seems like a reasonable thing to do.
In an assembly:
