Hi there,

I think that you are referring to Hanken cels. (Cels that
are used in the production of publication pieces, posters,
cd liners, etc. 
From what I read and seen in this forum, most genuine
Hanken cels have the trace lines hand painted on the acetate
rather than xeroxed like a production cel.
Also, hankens are rather expensive (upwards $1000 and up).

Hope that helps...I'm sure there are others here you can
elaborate more on this subject.

Regards,

Mark