@kenshirriff He was mostly there to talk Forth, but a bunch of us were curious about the device. He showed how he could chord the switches, enter different letters. He was pretty fast at typing with it. I'm positive, in retrospect, that he'd built himself an Englebart keyset, and had gotten good at using it. I appreciate your post for explaining a 45-year-old mystery to me! I did write some Forth code afterwards, but used a regular keyboard for it. 2/2