A Copyscope is a widefield refractor built from a surplus photocopier lens. These lenses are short focal length and have very flat fields. I assume that they are at least achromatic, especially if the lens is from a color copier.
Photocopier lenses tend to be mounted in aluminum cells.
I drew heavily from these magazines for my inspiration in building my Copyscopes. Where to get a photocopier lens I have two photocopier lenses that I've built into Copyscopes. It is unlabeled, and I haven't bothered to measure it. I got my first lens at went out of business years ago, and I haven't seen another ad in TSM for photocopy lenses in some time. There is good news though.