I use the term "Kid" in a complimentary way. He's a senior in college, computer science major, a really bright guy. He's the kind that rewrites FreeBSD kernels on weekends for fun. Give him a challenge, a supply of caffeine, and he'll program a few thousand lines of code by next morning.
Anyway he saw my HP67 in my office and was intrigued. This machine is older than he is, so I demonstrated. His first reaction was wow, how good the LED display is. The dialog went something like this:
"Yeah I remember reading about these, reverse something?"
"Reverse postfix notation. 2 ENTER 3 PLUS. Fewer keystrokes and you can see all the intermediate results"
He understood immediately. "How deep is the stack?"
"4 levels"
"ONLY 4?! Ha ha"
"Well memory was expensive back then."
"When was this made?"
"1978" (He was born in 1982.)
His eyes lit up. He played with it for a while and I think figured out most everything on it.
But he didn't notice the slot for the card reader. So I ran a card through it for him.
"WOW that's really cool! How much can you store on a card?"
"I'm not exactly sure, I think it's about 256"
"256 k?"
"No 256 bytes" Then I showed him my collection of program cards, Mathpak, Statpak, and a few others.
"That's amazing! I'd have no idea how to program that in 256 bytes."
Even old HP technology never fails to impress. I'm going to bring in my HP41CX with wand, printer, and card reader to show him.