Ok, I don't really understand what you mean by 
it being a book layer, but the photocopied part 
is on the bottom, replacing a second acetate 
layer.  The cel I have now is actually 2 layers 
stuck together, and the part that is the 
photocopy is NOT a background, and is an 
integral part of the overal image of the cel.  
There is actually no background whatsoever, 
which is why I cant understand why this 
photocopied layer can be called the background.

I am unsure as to whether it is a self-generated 
or studio-generated copy.  I would tend to 
believe it was not created by the studio because 
it is not a very good copy.