By the 60s, I was using "slide projectors," "opaque projectors," and "overhead transparency projectors" and traveled with a luggage cart to haul whichever projector and a bulging case with slides or folders filled with charts or transparencies for the one chosen.
I remember being blown away by a device with a revolving Polaroid lens which gave a flickering look (moving arrows or the like) to a static slide.
Now, of course, I lust for a pico projector with laser
. The whole thing can fit in a shirt pocket!
It is true, however, all the technology in the world can't make a bad presentation good.