It was about a foot square (or more), at least 3 inches thick, had a large handle to grip, a wired stylus, and a painfully low-res B/W LCD display. I got to handle it a few times, but saw no compelling use (the concept was great, but technology was far from there). IIRC, 3 came with a Wang minicomputer at the time, late 1980's or early 1990's.

I've tried to find a picture of it several times since, but nothing yet.