I once picked up a Rollie medium format projector from a flea market for $15. The reason it was so cheap was the zoom lens for the projector came in a bag of a dozen or so of glasses and an empty lens barrel. I figured in the worst case I would have to find a replacement lens for the projector.

Well, I tried all possible combinations of orders and the sides of all the glass pieces to reassemble the lens. Some of the glasses due to the size were obvious. So there weren't too many possible combinations to try. Within one hour I found a combination that would project a sharp image on the screen. I then cleaned each piece of glass and reassemble again. I have had a perfect Rollie MF projector ever since.

I guess to some people as soon as the lens is disassembled and the glasses mixed up it becomes a paper weight. Not really.