Apologies if this is not the right place to ask this.
When I was in high school in the early 90s (maybe 1992 or so), they took us on a field trip to what I think was a government R&D center of some sort. One guy showed us an optical mouse which had a transparent window with "crosshairs" on it. I believe that it was used to "trace" drawings or schematics that were on paper, so as to digitize them, or maybe aid in the creation of new drawings (the same guy showed us a large color plotter). I have no idea to what kind of system it was all connected. They also had some pretty old stuff at that place, like those big reel tape drives and 8" floppies (already obsolete back then), but they seemed to be somewhat proud of the plotter, and the optical mouse was ahead of its time.
I remembered this the other day while watching a YouTube video about a very early optical mouse. I tried googling, but I couldn't find anything like what I saw. Do keep in mind that I was a kid back then, and this was some 25 years ago, so my memories are probably less than perfect. Considerably less.
Does anyone know of any mouse or device like that?