I recently bought a copy of "Marvel Super Heroes" for the Saturn that was missing the manual, so I bought one of these replacement manuals to see how it is. It's decent quality, not great and certainly not TCP quality by any means. Small text is quite fuzzy. Replacement manual is a fraction of an inch shorter than an original - still fits between the notches of the longbox though.
I don't think these will ever be mistaken for originals. The print quality is far below originals, and original manuals have a perforated registration card attached to the inner back cover - these reproductions do not.