This means there is no "original illo" other than the inky stencil. It was a highly skilled art. Many fanartists did not attempt it — they drew their work on paper and then they or the faned traced it onto the stencil with the aid of a light table. That artwork was also said to be "handstencilled" as it would often be enhanced with shading or stylus work that would make the mimeographed artwork look much different from the original.
Once electrostencilling came in, even fewer fanartists attempted handstenciling. Instead, fanzine artwork was electrostencilled and then scissored out of the electrostencil and glued or cemented into a regular stencil, in which a hole of appropriate size was chopped. (This was done because electrostencils were much more expensive than regular stencils, and most faneditors had to pay for electrostencilling service, so they crammed as much art as possible onto a single stencil.)
Handstenciled artwork had a unique and distinctive style. The shading plates, stylii and other tools produced lines quite different from other drawing methods. The deceptively simple lines of cartoons by such artists as ATom and Rotsler were developed because it was easy to stencil and mimeograph but some handstenciled works were quite elaborate..