I'd have to say this is the most detailed sketch
that I have.  I don't think it is a sketch from a
cel, it isn't numbered so I guess it might be genga?

I don't normally buy sketches, but this one I
bought because of how detailed it is and what time
frame it came from :)

It came with 3 other sketches, 2 of his mouth and
one of his face without the hair.