There was a conventional field target sitting on a shelf cut behind the knot hole. You can see the regular target clamps in the picture, along with a second hold drilled for the reset string.
At the firing line you could see the KZ (3/8" at 11 yds, IIRC). The knot hole was big enough to see when the target properly fell over. But the knot hole wasn't big enough to tell what silhouette sat behind. Does anyone know what it was?