Here you go, Brad. High precision shadow projector with accurate scales for measureing parts.
Very cool chit. Very expensive new, MAYBE available on an auction from a machine shop going
out of business for a good price. Kinda a precision projection microscope with the lenses
and distances fixed to get accurate measurements on the screen scales. You can't see but there
are scales etched on the screen and you can move the part around on the stage with knobs, very
precisely to line up reference edges with the lines on the screen scale to measure stuff. Different
magnifications are available, often, and all are magnified so you can see much better what is
being measured.
I have no idea what Ian has there, but it looks interesting,hope he will share more info.