I have a 18" beseler lens from an opaque projector with minor edge chipping on one of the lenses. I was running a 15" with this lens, and the chipping did not affect the resulting image. You can see in the image looking through the lens, you cannot see the chips.

$40 shipped

Click to view attachment

Click to view attachment

Click to view attachment

The mark in this image is a dried water spot, which wiped right off.