David Griffith wrote:
There still is a variation of this in which a coin is placed in a niche in
front of a trap door. Angry buzzing is heard and a hand comes out of the
trap door and pulls the coin inside.
Google for ("magic hand" bank) and you'll find several websites selling
it.
Thanks for pointing that out, I did see that one years ago but had forgotten
about the coin-bank aspect. IMHO, the addition of the coin acquisition aspect
detracts from the original conception of Shannon/Minsky, but it's probably
that addition of a 'purpose' that has made it popular/long-lived.