I havne't read ALL the posts as of yet.  But, what
I am *thinking* you mean by photocopy is that
there is another layer on top of the cel that has
no paint on it, but the outline??

I actually have a cel that is a single layer, then
a photo copy later was placed on top of it.  This
came like that from the studio.  The reasons for
this is that sometimes, after a cel is made, the
trace lines (the outlines) are not strong enough.
 So to prevent having to redo the cel, the
animator would make a photocopy cel and place it
on top of the original to reinforce the black lines.

So, maybe that is what you are seeing.  If not,
then please show us a scan of the photocopy layer
that you are referring to in order to clear it up.

Star Phoenix