Following James Drummond, I find that usage "genuine counterfeit" passing strange. Not sure I could explain that to my 8 year old, but if that is how Scott calls 'em, so be it.
But how about that Scott statement "values for counterfeits on cover are for contemporaneous usage." Pegging the value now to face value then isn't it? Rather elegant solution that at a stroke removes them (Scott) from analyzing whatever marketplace(s) exists for counterfeits. I can understand they do not want for several reasons to create, nor facilitate, nor analyze the market(s) for counterfeits.
But I for one would not have been looking closely to a relatively modern 13 cent stamp shown in the example by redwoodrandy... except that it appears to be coil pair lacking vertical perforation and that lack is what formed the rationale for the ruse.