This was Peter Hajek's exchange puzzle at IPP29...
it is an unusual object... Original design from 1773! Recreated in 2009!
one handle turns the gears at one end, and the arrows on the wheel at the other all behave differently...
The "puzzle" is to explain the behavior, which isn't terribly difficult, but it is an interesting puzzling object...
I'm selling these puzzles because I no longer have space to store or display them :(
buyer is responsible for money transfer fees (ie 3.5% for paypal), packing and shipping expenses...