My father used this in teaching university courses. He retired and then gave it to me. Since then I have just kept it stored under its cover.
I recently tested it and found out it doesn't work quite perfectly:
* it will project onto the wall or a screen the way it is supposed to,
*but it will not project onto its little internal view-screen when flipping the lever to do that
as apparently the little mirror inside that diverts the projection has come unglued off its mount
A handyman could possibly disassemble it to reglue the mirror and get it to work in the other mode too.